For this problem, we can use the pythagorean theorem. The formula for that is:
a²+b²=c² where a and b are side lengths and c is the hypotenuse
Plug in the data that we know
7²+b²=8²
49+b²=64
subtract 49 from both sides
b²=15
b=√15
b=3.8729
round to the nearest hundredth
b=3.88 units
