Answer:
So we know the shop spent $250 on equipment and they also purchased 300 T-shirts for $2 each.
Knowing this, we only have to add to the $250, what they have paid for the T-shirts.
So if each T-shirt is purchased by $2 and they have bought 300, we multiply:
2 * 300 = $600
So we add the $600 spent on T-shirts to the $250:
600 + 250 = $850
We could also have done it with by replacing T for 300 in C = 2T + 250:
C = 2*300 + 250 --> C = 600 + 250 --> C = $850