Gas mileage is the number of miles you can drive on a gallon of gasoline. a test of a new car results in the 380 miles on 10 gallons of gas. how far could you drive on 55 gallons of gas?

question 1 options:

a. 79.6 miles

b. 2090 miles

c. 69.1 miles

d. 0.14 miles

There are two ways to solve this. One way is to use proportions:
380/10 = x/55
Cross multiply:
20900 = 10x
Divide:
x = 2090
Your answer is B

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.