Answer:90 bikes
Step-by-step explanation:they store cost $3600 to stay open eache month and the store buys a bike for $50 and then sells the bike for $90, so you would subtract 90 from 50 to see how much they are actually making when they cell a bike, they are making $40 everytime they cell a bike so you would divide 3600 by 40 to see how many bikes they would need to sell