Question 638451

Dear Sir/Mame, any assistance in the following question will be gratefully taken.
'Marty buys some stamps. He buys 50 cent and 75 cent stamps to the value of $12.50. Altogether, he buys 21 stamps. How many of each type of stamp does he buy?
Thank You,
Kind Regards,
Sash Lack


Let amount of 50c stamps purchased be F, and amount of 75c stamps, S


Then: F + S = 21 ----- eq (i)


Also, 50F + 75S = 1250 ----- eq (ii)
- 50F - 50S = - 1,050 ------ Multiplying eq (i) by - 50 ---- eq (iii)
25S = 200 ---- Adding eqs (iii) & (ii)


S, or amount of 75c stamps purchased = {{{200/25}}}, or {{{highlight_green(8)}}}


F + 8 = 21 ----- Substituting 8 for S in eq (i)
F = 21 - 8


F, or amount of 50c stamps purchased = {{{highlight_green(13)}}}


You can do the check, I'm sure!!


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