system of equations

[sarahilc]

an aparetment building contains 80 apartments. One-bedroom apartment rent for $850 per month. Two bedroom apartments rent for $1050 per month. The total monthly retal income is 78 400. How many apartments of each type are in the the building?
what i have so far:
let x represent number of one bedroom apartments
let y represent number of two bedroom apartments.
x+y=78400
x850+y1050=78400
what do I do next?

 

[Denis]

an aparetment building contains 80 apartments. One-bedroom apartment rent for $850 per month. Two bedroom apartments rent for $1050 per month. The total monthly retal income is 78 400. How many apartments of each type are in the the building?
what i have so far:
let x represent number of one bedroom apartments
let y represent number of two bedroom apartments.
x+y=78400
x850+y1050=78400
what do I do next?

There are 80 apartments; so x + y = 80 ; y = 80 - x [1]

Next equation ok, but show this way: 850x + 1050y = 78400 [2]

Substitute [1] in [2] : 850x + 1050(80 - x) = 78400
solve for x