First, we need to find the total amount they spent by adding 625 and 250 to get a total of $875. Then, we can divide the total amount by 5 to get 175 because each ticket sold will raise $5. We can write the formula 25x=175 to find how many tickets need to be sold per person. To solve for x, you would divide both sides by 25 to get x=7. Therefore, every student must sell 7 tickets.
I hope this helps.