Apost office sells first-class stamps and postcards stamps. for the year, the post office sold 7 first-class stamps for every 2 postcards stamps sold . the post office sold 46,260 stamps for a the year. how many of them were first-class stamps? how many were postcards stamps?

Since the post office sells 7 first-class stamps for every 2 postcard stamps, this means
that of every 9 stamps it sells, 7 are first-class.
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Therefore the ratio of first-class stamps to total stamps is 7 to 9 or 7:9. You are told
that the total of the stamps sold in a year is 46,260. With these figures we can now write
a proportion:
7 over 9 = x over 46260

in which x represents the number of first-class stamps sold in a year.
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You can begin to solve proportions by cross-multiplying ... that is by multiplying the numerator
of the left side times the denominator of the right side, multiplying the denominator
of the left side times the numerator of the right side, and then setting the two products
equal.