SCHOOL'S COST
The school's cost for the box of 25 shirts is $125, so each shirt costs the school $5 each.
$125/25 shirts per box= $5 per shirt
If 8 shirts are sold, it costs the school 8 times $5 a shirt. Everything above $5 per shirt is profit.
8 shirts * $5 per shirt school cost= $40 school cost for 8 shirts
SELLING PRICE
The students are selling the shirts for $10 each. One student sold 8 shirts for $10 each.
8 shirts * $10 each selling price= $80
FIND DIFFERENCE BETWEEN SELLING PRICE & SCHOOL COST
$80 selling price - $40 school cost= $40 profit
ANSWER: C) $40 profit
Hope this helps! :)