With me with this

find the unknown side length, x

b) sq. root of 65

use pythagorean theorem to solve
a2+b2=c2
3^2+b^2=5^2
9+b^2=25
b^2=16
b=4
apply to other triangle for second leg
7^2+4^2=c^2
49+16=c^2
65=c^2
sq root of 65= c

Answer is a not really sure tho