Respuesta :

Pythagorean Theorem: A^2 + B^2 = C^2 
We know A and C, let's find B by doing it backwards 

C^2 - A^2 = B^2 
4^2 - 7 (square root of 7 squared is just 7) = B^2 
16 - 7 = B^2 
9 = B^2