Answer:
12
Step-by-step explanation:
Pythagorean Theorem states that
a² + b² = c²
plug in your terms
9² + b² = 15²
81 + b² = 225
then subtract 81 from 225 to get your b²
b² = 144
then find the square root of 144
the square root is 12 because 12 x 12 = 144
