Solution to Homura's Math Problem

In episode 10 of Madoka Magica Homura is presented with a math problem she can't solve. Poor Homura, she has been in bed for the last 6 months and as soon as she goes back to school she has to face this!

Let's help her!
Homura-chan, the next time you go back in time, please check this before going to school!

This is Homura's problem:

and this is the solution:

Immediately before her problem, we are briefely shown another problem on the electronic whiteboard:

Everytime she goes back in time something changes. We don't want her to learn the solution to the first problem just to be asked to solve this one! Homura-chan, here is the solution to this problem:

By the way, the technological level of the world they live in seems slightly superior to our own, but the same can be said for the problems they get in school considering they should be 14 years old!

In episode 9 we learned about entropy and the heat death of the universe and now we get these math problems. If the awesome story and shocking moments were not enough!
This anime never ceases to amaze me :D

By the way, can anyone help me with the translation of the left side of the whiteboard in this image?

I am tempted to try, but unfortunately my japanese level is not good enough yet and it will take me some time!

Pdf version of the solutions, if anyone is interested XD