Question 996733
Donna bought Php 25 stamps and Php 50 stamps amounting to Php 1,750. If she has a total of 45 stamps, how many of each kind of stamp did she buy? 
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Quantity:: t + f = 45 stamps
Value::  25t + 50f = 1750 Php
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Modify for elimination::
t + f = 45
t + 2f = 70
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Subtract and solve for "f":
f = 25 (# of Php 50 stamps)
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t = 45-25 = 20 (# of Php 25 stamps)
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Cheers,
Stan H.
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