The figure forms a right triangle.
Apply Pythagorean theorem:
c^2 _= a^2 + b^2
Where:
c= hypotenuse = 97
a & b = the other 2 legs of the triangle = x and 65
Replacing:
97^2 = 65^2 + x^2
Solve for x:
9,409 = 4,225 + x^2
9,409-4,225 = x^2
5,184 = x^2
√5,184 = x
x = 72