P=2 (l+w)
we know P=284
we also know that l= w+50
so replace l in the equation with w+50
284=2 (w+50+w)
284=2 (2w+50)
divide both sides by 2
142=2w+50
subtract 50 on both sides
98=2w
divide both sides by 2
49=w
so width is 49, and we need to add 50 to it to find the length
l= 49 +50
l=99