Make them count jelly beans.
1200 = 100%
35% of 1200 = 420
1200 + 420 = 1620
There are 1620 students enrolled this year.
First, let's add all the x's.
x + x + x + x + x = 5x
5x - 1 + 1 + 1 + 1
Now, let's add together all the 1's that are being added (not the 1 that is being subtracted from 5x).
1 + 1 + 1 = 3
5x - 1 + 3
3 - 1 = 2
5x + 2
There's no way you can actually solve this unless you know the value of x; without x's value, this is as simplified as the expression is going to get.
Hope this helps!