We can make an equation. If enrollment 5 years ago is E, and it increased by 12%, and became 1,400, this equation is:

1.12E = 1400

Divide by 1.12:

E = 1400/1.12

The rest of the problem is just cancelling carefully. First multiply top and bottom by 100 to get rid of those pesky decimals:

140,000/112

Cancel 2 on top and bottom:

70,000/56

Cancel whatever you want but 7 jumps out at me:

10,000/8

Hopefully you know that a factor of 10 divided by 8 should resemble 1250 or something like that, but if you don't, just cancel 2 again:

5,000/4

Cancel 2 again:

2,500/2

We know that this is 1,250. Quick reality check: does this seem like a little less than 1400? Yes it does, and it's in the answer choices, so we're pretty sure we're right. So the answer is E.
_________________