Answer: y= (-1/5)x -4
First move the x over t the other side of the equation. Now we have 5y=-x-20. Next divide everything by 5 to get y= (-1/5)x -4
Each day it decrease $2. So just multiply $2 x 4 days. It changed a total of $8.
What I would do is subtract 12 from -5. Then you would have -17. Then you would add 4 and it would be -13. So your answer is:
<h2><em>
-13</em></h2>