Do 11/24 + 2/5. then subtract your answer from 240
No the side lengths of 9,12, and 18 doesn’t form a right triangle. Posted a picture showing all the side length that is a right triangle.
Simplify the radical by breaking the radicand up into a product of known factors in other words take the cube root of 27 then for the exponent 9 you divide by 3 get
3x^3