Petroleum motor oil is combination of natural oil and synthetic oil. it contains 4 liters of natural oil for every 7 liters of synthetic oil. in order to make 627 liters of petroleum oil, how many liters of synthetic oil are needed ?

answer:

640

step-by-step explanation:

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

5

step-by-step explanation: