Working on a study guide for a test, not sure how to work these problems out. Anyone mind showing me how to work them out?

Solve: 9+3/x = 2/x^2

The function F(X) = -x^2+46x-360 models the daily profit, F(X), in hundreds of dollars, for a company that manufactures x computers daily. How many computers should be manufactured to maximize profit? What is the maximum daily profit?

Find the domain of F(X)= x/x^2-16

Solve: 4^x+6=16

Solve: 3^2x+1=27

Solve: x^1/2-2x^1/4-15=0