HEEEEEELLLP FOR A MEDAL!!!!!!!!!!!!!!!!!

A family has two cars. The first car has a fuel efficiency of 30 miles per gallon of gas and the second has a fuel efficiency of 35 miles per gallon of gas. During one particular week, the two cars went a combined total of 1500 miles, for a total gas consumption of 45 gallons. How many gallons were consumed by each of the two cars that week?

Question

HEEEEEELLLP FOR A MEDAL!!!!!!!!!!!!!!!!!

A family has two cars. The first car has a fuel efficiency of 30 miles per gallon of gas and the second has a fuel efficiency of 35 miles per gallon of gas. During one particular week, the two cars went a combined total of 1500 miles, for a total gas consumption of 45 gallons. How many gallons were consumed by each of the two cars that week?

anonymous · Answer

i help u n u help me deal?

homeworksucks · Answer

One of you is doing systems of linear equations and the other Bernoulli Principles (calculus maybe?).. This might not work out

anonymous · Answer

yeah its gonna work

anonymous · Answer

30x + 35y = 1500
x + y = 45 --> x = 45 - y

now sub 45 - y in for x in the other equation
30(45 - y) + 35y = 1500
1350 - 30y + 35y = 1500
5y = 1500 - 1350
5y = 150
y = 150/5
y = 30 

now sub 30 in for y
x + y = 45
x + 30 = 45
x = 45 - 30
x = 15

check...
30(15) + 35(30) = 1500
450 + 1050 = 1500
1500 = 1500 (correct)

first car (x) used 15 gallons
second car (y) used 30 gallons