Question 196407
Perimeter of a Rectangle = 2*Length + 2*Width
You are told {{{Length = (2*Width) - 3}}}
So
{{{Perimeter of a Rectangle = 2*Length + 2*Width}}}
{{{36 = (2*(2*Width) - 3) + 2*Width}}}
{{{36 = 4*Width - 6 + 2*Width}}}
{{{42 = 6*Width}}}
{{{7 = Width}}}
If the Width = 7 cm, then the Length = (2*7)-3 = 14-3 = 11.

Check your answer
Does 11+7+11+7 = 36???