You kneed to find the slope of the line to make one parallel to it. you can do so by using the 2 coordinates they gave you: (-4, 0) and (4, -4).
Slope is change in y divided by the change in x.
The 'Y' changed from 0 to -4, so it went down 4.
The 'X' changed from -4 to +4, so it went up 8.
(-4)/(8) is -1/2.
You can put this into the slope-intercept formula (y = mx + b) to get y = -1/2x + b. This is not the full equation, however. To get there, insert the point that the new line needs to go through into this formula and solve for b.
The point is (2, 3), so x = 2 and y = 3.
(3) = -1/2(2) + b
3 = - 1 + b
+1 +1
4 = b
This means that the equation you need is y = -1/2(x) + 4