erasers cost $5 per carton and pencils cost $7 per carton.

Question

If an order comes in for a total of 15 cartons for $85.00, what number of cartons of erasers were bought?

Answer 1

10 cartons erasers were bought. 

 

Explanation : 

 

Let's call x the number of cartons of erasers and y the number of cartons of pencils 

 

Now we have the equation : 

 

  5x + 7y  = 85

 

y=15-x (the number of cartons of pencils equals the total received which is 15 minus the number of cartons of erasers)

 

Let's rewrite the equation " 

 

   5x+ 7(15-x) = 85

 

Let's expand it  : 

 

5x + 105 -7x= 85

 

Let's move the terms in x to the right and 85 to the left : 

 

105-85 = 7x-5x

 

20=2x

 

Le's divide both sides by 2 to solve for x 

x=10 . 

 

Hope that helps. Good luck.