tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?
form a ratio 1: 12 = 2: 8
find annual profit: $75,000/6 = $12,500
roi = annual profit/ initial investment
roi = $12,500/$15,000 or 83.3%