After adding 4 positive unit tiles to each side, we get:
3x - 4 + 4 = 2x + 5 + 4
3x = 2x + 9
which simplifies the original equation, because at the beginning there were independent terms at both sides of the equal sign and now all independent terms are on the right side (the +9 term). Notice that the other options don't give this result.
To solve the time for each class, you do 2.5 hours divided by 3. Then you take this value and multiply by 5 since there are 5 classes. After you do this, you should get 4.17 hours roughly.
