SOLUTION: Alyssa is buying miniature cars. She wants to buy 17 cars total for a big race she and her friends are having. Silver cars are $5 dollars each. Red cars are $7 dollars each. If she

Algebra ->  Equations -> SOLUTION: Alyssa is buying miniature cars. She wants to buy 17 cars total for a big race she and her friends are having. Silver cars are $5 dollars each. Red cars are $7 dollars each. If she      Log On


   

Question 1070949: Alyssa is buying miniature cars. She wants to buy 17 cars total for a big race she and her friends are having. Silver cars are $5 dollars each. Red cars are $7 dollars each. If she spends $111, how many red cars did she buy. Question=Write 2 equations s=silver and r=red.
Is this an equation i could use as an answer? 111=xR+yS
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
They mean for you to use r and s as your variables, like this:
r= number of red cars bought
s= number of silver cars bought.
The total number of cars bought is
r%2Bs=17 and that is one of your equations.
The other one deals with the amount spent buying those cars.
The r red cars costed $7%2Ar .
The s silver cars bought costed $5%2As .
The amount Alyssa spent buying all those cars was $111, so
7r%2B5s=111 , and that is the other equation you need.
You need to solve the system of linear equations
system%28r%2Bs=17%2C7r%2B5s=111%29 <---> system%28s=17-r%2C7r%2B5s=111%29
but if you only need the value of r ,
substituting 17-r for s in 7r%2B5s=111
will give you an equation that you can solve for r :
7r%2B5%2817-r%29=111
7r%2B85-5r=111
2r%2B85=111
2r=111-85
2r=26
r=26%2F2
highlight%28r=13%29