In this case, we'll have to carry out several steps to find the solution.
Step 01
Data
supplier charges = $100 + $4 per pizza
cost of sale of band members = $7 per pizza
x = # pizzas
x = ? to make a profit
Step 02:
To make a profit :
7 x > 100 + 4x
7x - 4x > 100
3x > 100
x > 100 / 3
x > 33.33
The answer is:
The band members must sell 34 pizzas to make a profit.