SOLUTION: A stamp collection consists of 5, 13, and 18 cent stamps. The number of 13 cent stamps is one less than twice the number of 5 cent stamps. The number of 18 cent stamps is five mo

Question 132790: A stamp collection consists of 5, 13, and 18 cent stamps. The number of 13 cent stamps is one less than twice the number of 5 cent stamps. The number of 18 cent stamps is five more than the number of 13 cent stamps. The total value of all the stamps is $2.60. Find the number of 13 cent stamps.
Answer by checkley71(8403) (Show Source): You can put this solution on YOUR website!
X=NUMBER OF .05 STAMPS
2X-1=NUMBER OF .13 STAMPS
(2X-1)+5=NUMBER OF .18 STAMPS
.05X+.13(2X-1)+.18[(2X-1)+5]=2.60
.05X+.26X-.13+.36X+.18(2X+4)=2.60
.05X+.26X-.13+.36X+.18X+.72=2.60
.67X=2.60+.13-.72
.67X=201
X=2.01/.67
X=3 IS THE NUMBEER OF 5 CENT STAMPS
2*3-1=6-1=5 IS THE NUMBER OF 13 CENT STAMPS.
5+5=10 IS THE NUMBER OF 18 CENT STAMPS
PROOF:
.05*3+.13*5+.18*10=2.60
.15+.65+1.80=2.60
2.60=2.60
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