Question 333134
Use a^2 + b^2 = c^2.

We are given b and c but not a.  We are looking for side a.

a^2 + (4sqrt[2])^2 = 9^2

a^2 + 32 = 81

a^2 = 81 - 32

a^2 = 49

sqrt[a^2] = sqrt[49]

a = 7

The missing side is 7.