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An office has some 20¢ stamps and some 28¢ stamps. Altogether the office has 210 stamps for a total value of $47.60.
How many of each type of stamp does the office have?
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Solution 1. One equation in one unknown
Let x be the number of the 20c stamps.
Then the number of the 28c stamps is (210-x).
A "value" equation is
20x + 28*(210-x) = 4760. (1) (4760 = $47.60 )
Simplify and solve for x.
Solution 2. System of two equations in two unknowns
x + y = 210, (1)
20x + 28y = 4760. (2)
From (1) express y = 210-x and substitute it into (2). You will get and equation
20x + 28*(210-x) = 4760. (3)
It is identical to the equation (1) in the Solution 1 above.
Simplify it and solve for x.
After finding x calculate y.
