Now lets write the information that we know form the problem given:
We are told that the Perimeter = 30 inches
We are told that the Length is 3 inches less than twice its width. So lets rewrite this one into the equation. The length (L) is equal to (=) 3 inches less (-3) than twice its width (2W). Therefore, L = 2W-3
So now we have an equation to plug in for L and we still do not know what W is
Next, Plug into the equation!
P = 2L + 2W
30 = 2 (2W-3) +2W
Now Solve!
30 = 2 (2W-3) +2W
30 = 4W-6+2W
+6 +6
36 = 4W + 2W
36 = 6W
6 = W
Now we know what W is we can plug in to find L
P = 2L + 2W
30 = 2L + 2(6)
30 = 2L + 12
-12 -12
18 = 2L
9 = L
The length of the rectangle is 9 inches!