Answer:
a =12sqrt(2)
Explanation:
The Pyhtagorean theorem is a^2 +b^2 =c^2
where a and b are the legs of the triangle and c is the hypotenuse
We know one of the legs is 6 and the hypotenuse is 18.
a^2 + 6^2 = 18^2
a^2 +36 =324
Subtracting 36 from each side
a^2 +36-36 = 324-36
a^2 =288
Taking the square root of each side
sqrt(a^2) = sqrt(288)
a =sqrt(288)
Knowing sqrt(ab) = sqrt(a) sqrt(b)
a = sqrt(144)sqrt(2)
a =12sqrt(2)