To answer this question you must use Pythagorean theorem
a and b are the legs (the sides that form a perpendicular/right angle)
c is the hypotenuse (the side opposite the right angle)
In this case...
a = 3
b = unknown
c = √34
^^^Plug these numbers into the theorem
Simplify
9 + b² = 34
solve for b
= 25
Take the square root of both sides to cancel out the square from the b
√b² = √25
b = 5
Hope this helped!
~Just a girl in love with Shawn Mendes