The function for the cost of materials to make a muffin is f(x) = three fourths x + 3, where x is the number of muffins. the function for the selling price of those muffins is g(f( where g(x) = 3x + 4. find the selling price of 20 muffins.

Hello,

Let's do this problem 1 step at a time.
What you want to do is plug in the number of muffins (20) into f(x), and then plug the value you get into g(x).

For f(x), you get
(3/4)(x) + 3   = (3/4)(20) + 3 = 15 + 3 = 18
So, f(x) = 18

You then plug in the value of f(x) (18) into g(x)
This is 3(x) +4 = 3(18) + 4 = 58
The selling price of 20 muffins would be 58 (dollars?). Don't forget to include units!

Hope this helped!