The expression for T-shirt production is 20+9T
The expression for total price of selling the T-shirts is 15T
Profit = Total cost of selling - Total cost of buying
Profit = 15T - (20+9T)
Profit = 15T - 20 - 9T
Profit = 6T - 20
To make profit ≥150
6T - 20 ≥ 150
6T ≥ 170
T ≥ 170/6
T ≥ 28.3
The minimum number of T-shirts needed is 29 T-shirts
