Number of t-shirts: x
Multiply the number of t-shirt for the cost of each one of it to find the earns of sold that number of t-shirts: 14.50x
Then, the earns of sold x number of t-shirts and the $850 they've raised needs to sum at least 2400 (at least means greather than or equal to 2400)
Then, you get the next inequality:

To solve the inequality:
1. Substract 850 in both sides of the inequality:

2. Divide both sides of the inequality into 14.50:

Thenm, to meet the goal, they need to sold a number of t-shirts greather than or equal to 107 (as you can not sold 0.89 t-shirts)