Okay, so we have a rectangle of the sandbox inside a larger rectangle of the grass. We're asked for dimensions of the sandbox, so we'll make a variable W for sandbox width and L for sandbox length.
From the prompt, the length of the sandbox is 2 feet more than width. Algebraically: L = 2+W
The grass is 4 feet out from all sides of the sandbox. So bigger rectangle width is W + 4 (left) + 4 (right) = W+8 and length is 2+W + 4 (above) + 4 (below) = W+10.
Now we can set up an equation for area in terms of a single variable W.
Area = length * width
142 = (W+10)(W+8)
Distribute and simplify.
142 = W^2 + 18W + 80
0 = W^2 + 18W - 62
Running quadratic formula, we get W~3 and W~-21.
Thus Width is about 3 and Length is about 5.
