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Four apps and two e-books cost $18. Five e-books and three apps cost $31. What is the cost of one app?

 Apr 11, 2021
 #1
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4a + 2e  = 18

3a  + 5e =  31       multiply first equation by -2.5 to get

-10a -5e = -45       add bottom two equations ( this will eliminate the 'e' variable)

- 7a = -14

a = 2 dollars

 Apr 11, 2021

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