<PRE><B>Question 132790</B>
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</PRE>