Question 232882
i'll use L for length and W for width.

you are given that L=2W-20.

and you need 2 lengths and 2 width to form a rectangle, so.

2W+2(2W-20)=140

2W+4W-40=140

6W=180

W=30

so width equals 30, now plug this in to the 1st equation to solve for L

L=2(30)-20

L=60-20

L=40