Question

A rectangle is 80 inches long. The diagonal is 100 inches.

Answer 1

I assume you are asking for the width of the rectangle
If so, use Pythagorean Theorem, a^2+b^2=c^2
80^22+b^2=100^2
6,400+b^2=10,000
b^2=3600
b=60
so the width equals 60in

Answer 2

The answer is the width is 60 inches long