Awesome!!! so his tools and stuff cost $80 and 6.25 PER BIRD HOUSE. To make a profit he needs to make more that 80 and 6.25+. And he'll sell the bird houses for $16. So we'll multiply. 16x (blank)=. And make it more than 80. Step 2. Let's say that you've got 5 bird houses. Now you have to mutliply 6. 25 and 5 because Juan had to pay that extra 6.25 per bird house.