Question 774755
{{{L=4W}}} This is another way of saying that the length (L) is four times the width (W).

{{{P=2(L+W)}}} This is the formula for the perimeter of a rectangle (P is the perimeter).

{{{30=2(L+W)}}} Since we know the perimeter is 30, we can plug in 30 for P.

{{{30=2(4W+W)}}} Now we can plug in 4W for L, since L=4W.

{{{30=2(5W)}}} We can combine 4W and W to get 5W.

{{{(30)/(2)=(2(5W))/(2)}}} To isolate W, we can divide both sides by 2.

{{{(15)/(5)=(5W)/(5)}}} To further isolate W, divide both sides by 5.

{{{3=W}}} Now you know what W is.

{{{L=4*3}}} Plug in 3 for W to calculate L, since L=4W.

{{{L=12}}} Now you know both W and L.

So the length is 12 and the width is 3. Don't forget to include the units, like inches, feet, meters, etc.  


And that's all there is to it!!!