Final answer:
To determine how much cable is left after Persis cuts off 12 feet 9 inches from 18 feet of cable, convert all measurements to inches, subtract the cut-off length from the total length, and you find that she has 63 inches of cable left.
Step-by-step explanation:
Persis has 18 feet of cable. We need to find out how much cable she has left after cutting off 12 feet 9 inches. To solve this, let's convert everything to inches first. There are 12 inches in a foot, so Persis initially has 18 feet * 12 inches/foot = 216 inches of cable.
Now she cuts off 12 feet 9 inches. We already know there are 12 inches in a foot, so 12 feet equals 12 feet * 12 inches/foot = 144 inches. Adding the extra 9 inches, she cuts off 144 inches + 9 inches = 153 inches in total.
Subtract the length of cable she cuts off from the initial length to find out how much is left. 216 inches - 153 inches = 63 inches. Therefore, Persis has 63 inches of cable left after hooking up the television.