Hey! Can someone help me?

What is the value of the expression below? (81^2)^1/8

Which of the following represents a number squared is equal to twenty more than nine times that number ? a) x squared = 9x + 20 b) x squared = 20x + 9 c) x squared > 9 + 20x d) x squared = 9 + x + 20

What value of x will make the triangles similar by the sss similarity theorem?