The equation we can use is
3 + 1/4c = 9
To find the total number of pieces, we would just solve the equation.
3 + 1/4c = 9
3 - 3 +1/4c = 9 - 3
1/4c = 6
inverse of division is multiputcation
4/1 *1/4c = 6*4
c = 24
There were 24 pieces of cake in total.