Let's say the width is (x) and the width is (x+12). The formula for a perimeter of a rectangle equals 2w + 2l, which would then for this problem be 100=2(x) + 2(x+12) which would distribute as 2x + 2x + 12 which equals 4x+12. When you subtract twelve from 100 you get 88=4x. Divide 88 by 4 and you get x=22. This then would mean the width is 22 and the length is 34. The formula for an area of a rectangle is w*l. Plug in the numbers that you figure out from the area formula and you get 22x34=748