Question 594387
Find the length and width of a rectangle with the length being 3 cm less than twice the width. The parameter is 36. 
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Since they don't tell you the width, create a variable to hold it:
Let W = width
then from "the length being 3 cm less than twice the width" we get
2W-3 = length
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P = 2L+2W 
36 = 2(2W-3)+2W 
dividing both sides by 2:
18 = (2W-3)+W 
18 = 3W-3
21 = 3W
7 cm = W (width)
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Length:
2W-3 = 2(7)-3 = 14-3 = 11 cm