Q: Jim decides to open up a bike shop. The most common repair he does is fixing bike tires. He charges $20 for this and it cost him $5 in parts. In one month Jim does 300 of these repairs. He also does 2 more complex repairs for $300 each and cost $50 in parts. He also sells $2000 profit worth of things from his retail shop. If rent and other fixed expense for the shop is $4000 a month how much profit did the shop make?
A: From each tire repair, he made 20 - 5 = $15 profit. So repairs made him a profit of 15 * 300 = $4500. The two complex repairs each made him 300 - 50 = $250 profit. So those added 250 * 2 = $500. So his total profit from everything was 4500 + 500 + 2000 = $7000. So he made a profit of 7000 - 4000 = $3000. The answer is 3000.

Q: It took Dad 5 more than twice as long to vacuum upstairs then to vacuum downstairs. He vacuumed for a total of 38 minutes. How many minutes did he vacuum upstairs?
A: Let D = time in minutes to vacuum downstairs. Upstairs = 2D + 5 minutes. 3D + 5 = 38. 3D = 33. D = 11 minutes. Upstairs = (2 * 11) + 5 = 27 minutes. Dad took 27 minutes to vacuum upstairs. The answer is 27.

Q: Darryl is an inventor who just designed a new machine. He had to pay $3600 for the parts to construct the machine, and $4500 for the patent he applied for once he built it. If the machine sells for $180, how many machines does Darryl need to sell to break even after the costs?
A:
Darryl paid 3600 + 4500 = $8100 in costs for the parts and patent. Thus, Darryl needs to sell 8100 / 180 = 45 machines to break even. The answer is 45.