Question 730849
Let

x = # of coupons Joe has


y = # of coupons Melissa has



We are told that "melissa has 5 more coupons than joe to give out", so we can say


y = x + 5


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Joe has 3 free hour coupons. So if he has x of them, then he has 3x hours free total. 


Similarly for Melissa, she has y 4-hr free coupons. This gives her a total of 4y free hours.


In total, they have 3x + 4y free hours. This total equals 90 hours (given), so...


3x+4y = 90 


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Now use these equations to find x and y


3x+4y = 90 


3x+4(x+5) = 90 ... plug in y = x+5


3x+4x+20 = 90


7x+20 = 90


7x = 90-20


7x = 70


x = (70)/(7)


x = 10


y = x + 5


y = 10 + 5


y = 15


To sum things up, we found that


x = 10 and y = 15


So Joe has 10 coupons and Melissa has 15 coupons