On a piano, the ratio of black keys to white keys is 9 to 13, if there are 88 keys on a piano how many are black?

Use the quadratic formula to solve 5x=6x^2-3,what are the values of x?

The perimeter of a triangle is 69 cm. the first is 5 cm shorter than the second side. the third side is twice as long the first side. find the length of each side

Let f(x) = x+3 and g(x) = 1/x the graph of (fog)(x) is shown below what is the range of (fog)(x)?