Answer:
C 6
Explanation:
Pythagoras
c² = a² + b²
117 = x² + (x+3)² = x² + x² + 6x + 9 = 2x² + 6x + 9
=>
108 = 2x² + 6x
54 = x² + 3x
0 = x² + 3x - 54 = (x-6)(x+9)
just think by what numbers can we divide 54 without any remainder (so that when multiplying we get 54) ? and which pair of these have a difference of 3 (so that with +/- combination we get "3x" in the multiplication)?
the solutions for x are the 2 numbers that would make one of the bracket expressions 0, as this turns the whole expression to 0.
x = 6 and x = -9
a negative number does not make any sense for a side length.
so, the only possible solution is x = 6