Answer:
16
Step-by-step explanation:
Using pythagorean theorem:
20^2 - 12^2 = x^2
400-144 = x^2
x^2 = 256
x=16
Use the Pythagorean Therom:
A^2 + B^2 = C^2
A=x
B=12
C=20
20^2 - 12^2 = 256
Square root of 256 is 16
