Solution for 3/4x - 12 = -18?

Pls yall i really need the answer fr fr

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)

Yolanda wanted to buy a total of 6 pounds of mixed nuts and dried fruit for a party she paid 21.60 for mixed nuts and 11.90 for dried fruit did yolanda but enough mixed nuts and dried fruit for the party