SOLUTION: 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

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!
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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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