Answer: -2
I'm not so sure what it means by slope, but because I saw a pattern between x and y (it decreases by 2 every x value and decreases by 4 every TWO x values) values so I would pick -2. BUT I don't know if the answer is -4.
Step-by-step explanation:
X/4 = 2.....x = 8
x - 9 = 17....x = 26 <=== there is the odd ball
x + 12 = 20....x = 8
2x = 16....x = 8
X - $5 bills
y - $10 bills
x + y = 12
y = 5x
x + (5x) = 12
6x = 12
x = 2
y = 5(2)
y = 10
10 $10 bills and 2 $5 bills