I need help with part b of this question.

A racquetball club charges $15 per month plus $6 for each hour of court time, and only whole numbers of hours of court time can be purchased. Let x be the number of hours of playing racquetball in a given month, and g(x) the total cost.

a. Write an equation for the cost per month of playing racquetball?
g(x) = 6x + 15

b. What is the value of g (14)?
What would the equation be for this.I know the answer is $99

notice on the left g(x) has become g(14)
so the x was replaced by 14
Now do the same thing on the right side of the equation, you will be amazed at the result.

thank you.