SOLUTION: a girl bought 20 first-class stamps and 10 postcard stamps for $11.10. another day she spent $24.50 on 40 first-class stamps and 30 postcard stamps. find the cost of each type of s

Question 1030737: a girl bought 20 first-class stamps and 10 postcard stamps for $11.10. another day she spent $24.50 on 40 first-class stamps and 30 postcard stamps. find the cost of each type of stamp
Answer by Cromlix(4381) (Show Source): You can put this solution on YOUR website!
Hi there,
Make first class stamps = x
and postcard stamps = y
20x + 10y = 1110.......(1)
40x + 30y = 2450.......(2)
Multiply Eq(1) by 3
60x + 30y = 3330.......(1)
40x + 30y = 2450.......(2)
Subtract Eq(2) from Eq(1)
20x = 880
x = 44
Substitute x = 44 into Eq(2)
40x + 30y = 2450.......(2)
40(44) + 30y = 2450
1760 + 30y = 2450
30y = 2450 - 1760
30y = 690
y = 23.
First class stamps cost $0.44
Postcard stamps cost $0.23
Hope this helps :-)
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