Charlie's weight is represented by the expression x+9. Since the equation needs their weights totaled, you must add x and x+9 and set it equal to 99 to get *2x + 9 = 99*
Total money=$120 on shirt=$25.65 on socks=$7.98 on a cd=$16.23 on snack=$4.58 so total money left=total money-total money spent =$120-($25.65+$7.98+$16.23+$4.58) =$120-$54.44 so total money left=$65.56