Question

phillip bought 12 used cds and dvds.cds cost $2 each,and dvds cost $3 each.he spent $31,not including tax.how many dvds did phillip buy?

Answer 1

Let c and d be the number of cds and dvds respectively.

c+d=12

c=12-d

The we are told that:

2c+3d=31, using c found above in this equation gives you:

2(12-d)+3d=31

24-2d+3d=31

24+d=31

d=7

So Phillip bought 7 dvds.

check...

3*7+2(12-7)=31

21+2(5)=31

21+10=31

31=31