The length of a rectangle is 6 times longer than the width. The perimeter is 42 what is the width

Perimeter = length + length + width + width

if the perimeter is 42 then:

42 = length + length + width + width

if the length is 6 times the width, then

6 x width = length

42 = (6 x width) + (6 x width) + width + width

(i'm just going to start using w to represent width to make it easier

42 = 6w + 6w + w + w

combine all the w's

42 = 14w

divide both sides by 14

w = 3

the width is 3