So,
I like to simplify a fraction first. This is what I do when I'm in a store trying to find the unit price.

Factor.

Cross out ones.

Multiply it out.

In my head, I remember that one-eighth is equal to 0.125.
So seven-eighths is equal to 0.125 times 7.
0.125 * 7 = 0.875
Convert to percent form.
0.875 --> 87.5%
James answered 87.5% of his quiz correctly.
I actually have the decimal equivalents for eighths in my head when I'm shopping. So once I get seven-eighths, I immediately know how much that is. I can also subtract 0.125 from 1.000 to get seven-eighths.
Step-by-step explanation:

Supplementary angles, when added, equal 180 degrees
so < A + < B = 180...and if < A = 80
80 + < B = 180
< B = 180 - 80
< B = 100 <==
As the width gets larger so does the total area