Answer:
9
Step-by-step explanation:
We're using the Pythagorean theorem here since it's a right triangle.
a^2 (side) + b^2 (side) = c^2 (hypotenuse)
12 = a
x = b
15 = c
12^2 + b^2 = 15^2
144 + b^2 = 225
- 144 - 144 (subtracting 144 from both sides to isolate b)
b^2 = 81
[tex]\sqrt{b^2} = \sqrt{81}[/tex] (getting rid of the exponent by squaring both sides)
b = 9
x = 9
