Since this is a right triangle, we can use the Pythagorean theorem
a^2 + b^2 = c^2 where a and b are the legs and c is the hypotenuse
5^2 + 3^2 = c^2
25+9 = c^2
34 = c^2
Taking the square root of each side
sqrt(34) = c
Rounding to the nearest tenth
c =5.8