math
posted by Lorraine on .
suppose you own a card shop. you buy one line o cards at a rate of 4 cards for $5. You plan to sell the cards at a rate of 3 cards for $5. How many cards must you sell in order to make a profit of $100?

Profit = Sale  Cost
100 = (5/3)o  (5/4)o
Simplify and solve for o