When you miss a prayer unintentionally and your excuse is either forgetting or sleeping, although you are basically very keen to perform the prayer on time, then you just have to make it up as soon as you remember it.
It is narrated in Sahih Muslim (681): Which relates how the Prophet (ﷺ) and his companions slept and missed Fajr prayer, and the Sahabah began to ask one another: “What is the expiation for what we have done by neglecting the prayer?” The Messenger of Allah (ﷺ) said: “Sleeping does not mean that you are neglecting the prayer. Rather neglecting the prayer means not praying one prayer until the time for the next prayer comes. Whoever does that let him pray when he remembers it.”
In the case of your situation with the tuition (university, work, school, etc.): You should make sure that you schedule your tuition or courses if possible in such a way that you pray either before or that you surely know if it will not claim too much of your time so as that you would miss your prayer.
If you have no possibility whatsoever to pray before your tuition (or course, etc.) and you made sure to absoultely take everything into consideration, but you could not, then you can join the Dhuhr and Asr prayer (or Maghrib/Isha). When you join the prayers, you can for example according to your time of not making it, join the Dhuhr prayer when it is already Asr.
The evidence for that is narrated in Sahih Muslim (705b):
The Messenger of Allah (ﷺ) observed the noon and afternoon prayers together in Medina without being in a state of fear or in a state of journey. (Abu Zubair said: "I asked Sa'id [one of the narrators] why he did that." He said: "I asked Ibn 'Abbas as you have asked me, and he replied that he [the Holy Prophet] wanted that no one among his Ummah should be put to [unnecessary] hardship.)
Note that you can not do that on every occasion just because you think that a "small issue" (which can be solved by considering the situation properly and to exploit every possibility e.g. to pray shortly outside somewhere while having time to reach the tuition) would give you permission to use this kind of relief all the time. And doing this for every little occasion without considering every outcome will not be accepted.
If you missed one prayer intentionally, therefore knowing that you could have made it, it is not valid for you to make it up according to the more correct view of the scholarly opinions, rather you have to repent and regret it, and resolve not to do it again. You should do a lot of good deeds and offer voluntary prayers.
Abu Bakr (rn) narrated: I heard the Apostle of Allah (ﷺ) saying: "When a servant (of Allah) commits a sin, and he performs ablution well, and then stands and prays two rak'ahs, and asks pardon of Allah, Allah pardons him." He then recited this verse [Qur'an 3:135]: "And those who, when they commit indecency or wrong their souls, remember Allah" - End Quote of the Hadith - [...] and seek forgiveness for their sins - and who can forgive sins except Allah? And [who] do not persist in what they have done while they know." Narrated in Abu Dawud (1521) and Sheikh Albani classed it as Sahih
I found Allah's Messenger (ﷺ) stand and address the people. I heard these words of his: "If any Muslim performs ablution well, then stands and prays two rak'ahs setting about them with his heart as well as his face, Paradise would be guaranteed to him." I said: "What a fine thing is this!" And a narrator who was before me said: "The first was better than even this." When I cast a glance, I saw that it was 'Umar who said: "I see that you have just come and observed: If anyone amongst you performs the ablution, and then completes the ablution well and then says: I testify that there is no god but Allah and that Muhammad is the servant of Allah and His Messenger, the eight gates of Paradise would be opened for him and he may enter by whichever of them he wishes." Sahih Muslim (234a)
Verily the Messenger of Allah (ﷺ) said and then narrated (the hadith) like one (mentioned above) except (this) that he said: He who performed ablution and said: "I testify that there is no god but Allah, the One, there is no associate with Him and I testify that Muhammad is His servant and His Messenger." Sahih Muslim (234b)