I believe this is a problem dealing with proportions, so you could cross multiply and divide. so you would do 8/270 then x/72.5 , you cross multiply 72.5x8 which equals 580. then you divide that answer by 100 which equals 5.8 (:
(1073 + 1108 + x) / 3 = 1000 (2181 + x) / 3 = 1000 ....multiply both sides by 3 2181 + x = 1000 * 3 2181 + x = 3000 x = 3000 - 2181 x = 819 <== they would need to earn $ 819 on Sunday
