l = 3w,2(l+w)>48, l>?

l = 3w, 2(l+w)>48, l>?

Substitute   3w for l and we have

2( 3w + w) > 48      simplify

2 * 4w  > 48

8w >  48       divide both sides by 8

w  >  6

But, l = 3w     means that   l / 3  = w.....so

l / 3  >  6      multiply both sides by 3

l  >  18