Question 1188695: A man bought a number of 12p stamps and also sufficient 16p stamps to make his total expenditure £4.80. If, instead of the 12p stamps, he had bought three times as many 8p stamps he would have needed 9 fewer 16 stamps than before for his expenditure to be £4.80. Find how many 12p Stamps he bought.
Answer by ikleyn(52787)   (Show Source):
You can put this solution on YOUR website! .
A man bought a number of 12p stamps and also sufficient 16p stamps to make his total expenditure £4.80.
If, instead of the 12p stamps, he had bought three times as many 8p stamps he would have needed 9 fewer
16 stamps than before for his expenditure to be £4.80. Find how many 12p Stamps he bought.
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x = the number of the 12p stamps;
y = the number of the 16p stamps.
Write two equations as you read the problem
12x + 16y = 480 (1)
8*(3x) + 16(y-9) = 480 (2)
Simplify to the standard form system of linear equations.
12x + 16y = 480 (3)
24x + 16y = 624 (4)
Subtract equation (3) from equation (4) to eliminate the terms with "y"
12x = 624 - 480 = 144
x = 144/12 = 12.
ANSWER. The man bought twelve 12p stamps.
Solved.
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