It's a perfect square because 8 times 8 equals 64.
Answer:
1. 2x + 5y = 5
2. 3x + 2y = -9
Step-by-step explanation:
The function will be

where y is the balance, and x is the number of month.
The raph will be a line on the xy-plain which starts at the point (0, 360), and end in the point (72, 0).
Hope it helps.
If the order matters it is a permutation. For example: if you are selecting 3 people to be on a committee it doesn't matter what order you select them, but if you're selecting three people to be president, vice president, and secretary the order in which you choose them matters the first person being president, the second person being vice president, and the third person be secretary