The perimeter of a rectangle is 42 cm. The length is 3 more than twice the width. Find the length and Width of the rectangle

Question

I have to slove by system of equations 

Answer 1

P=2l+2w

42=2l+2w

l=2w+3

simplify the first equation

21=l+w

substitute

21=2w+3+w

21=3w+3

21-3=3w

18=3w

w=18/3

w=6 cm

21=l+6

l=21-6

l=15 cm