What is the value of the expression 3x+9 if x=6

Just tell me how to set up the equation.

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8

If you flip a coin 3 times, what is the probability of flipping heads 3 times? a. p(3 heads) = 3/8 b. p(3 heads) = 1/6 c. p(3 heads) = 1/8 d. p(3 heads) = 1/2