Answer:
26.8
Step-by-step explanation:
We can use the Pythagorean theorem
a^2+b^2 = c^2
where a and b are the legs and c is the hypotenuse
12^2+ b^2 = 18^2
144+b^2 = 324
b^2 = 324-144
b^2 = 180
Taking the square root of each side
sqrt(b^2) = sqrt(180)
b = 13.41640
We know b = 1/2x
2b =x
2(13.41640) =x
26.83281573 =x
26.8
