bearing in mind that a solution to a system of equations is where their graph intersect or meets, Check the picture below.
(4,9) is in quarter I and (4,-9) is in quarter IV of the graph. (4,-9) is the point (4,9) reflected over the x-axis. they are similar bc both have 4 as their x coordinate.
First we need to find the length. So we do 126/3 to get 42. The length is 42. Now to find perimeter we do 2(42)+2(3) or 42+42+3+3.
Both ways are right ways. The perimeter is 90 meters.
Hope that helps!!