Question

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(x)), where g(x) = 3x + 4. Find the selling price of 20 muffins.

Answer 1

f(x)=3/4 x+3
g(x)=3x+4

The new function g(f(x)) will be:
g(f(x))=3(3/4 x+ 3)+4
g(f(x))=9/4 x+9 +4
g(f(x))=9/4 x +13

If x=20; then :
g(f(20))=(9/4)(20)+13
g(f(20))=45+13
g(f(20))=58

Answer: the selling price of 20 muffins will be $58.