What multiplication sentence equals 23

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 values of x satisfy the inequality x^2-9x< 0? how is your answer shown on the graph?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).