Joshua has a brand of peanut oil, which has 19% oil. Kyle has a brand of olive oil, which has 71% oil. Joshua and Kyle combined their oils and made 1 3/10 quarts of a new oil. If the new oil containes 39% oil, how many quarts of peanut oil did they use?
Let the amount of peanut oil = x quarts
Then the amount of olive oil = (1.3 - x) quarts
Then we can solve this equation
.19x + .71 ( 1.3 - x) = .39 ( 1.3) simplify
.19x + .923 - .71x = .507
(.19x - 71x) = .507 - .923
-.52x = -.416 divide both sides by -.52
x = .8 (quarts of peanut oil used)