math
posted by jazmyn .
A vendor at a concert sells new and used CDs. The new CDs cost 2.5 times as much as the old CDs. If 4 used CDs and 9 new CDs cost $159, what is the price of each item?

old cds = x
new cds = 2.5x
4old cds + 9 new cds = 159
4(x) + 9(2.5x)=159
4x+22.5x=159
26.5x=159
x=6 so old cds cost $6.
and new cds cost 2.5(6)=$15.
Check:
4(6)+9(15)=159
24+ 135 =159
159=159