It's the first one. y can equal x as long as y doesn't equal x multiple times. We also know the last two are wrong because they're saying the same thing. A linear function is a straight line.
Subtraction: 18 - b
Addition: 18 + b
Multiplication: 18b, or 18 x b
Division: 18 divided (My keyboard doesn't have a division sign?) by b
Hope this helped.
200 dollars is equivalent to 40%
So what is 100% equivalent to;
Rent payment=

= 500 dollars
#2
2x - 4y = -2
2x + 3y = -16
------------------subtract
-7y = 14
y = 14/-7
y = -2
2x - 4y = -2
2x - 4(-2) = -2
2x + 8 = -2
2x = -2 -8
2x = -10
x = -10/2
x = -5
answer x = -2 and y = -5
check:
2(-5)- 4(-2) = -2
-10 +8 = -2
-2 = -2.....true
2x + 3y = -16
2(-5)+3(-2) = -16
-10 + (-6) = -16
-16 = -16...true