Question

The length of a rectangle is 3.9 cm more than 3 times the width. If the perimeter of the rectangle is 32.6 cm, what are its dimensions?

Answer 1

So length is 3.9 cm more than 3 times the width
perimeter is 32.6 cm
 l = 3w + 3.9

P = l + l + w + w
32.6 = 3w + 3.9 + 3w+ 3.9 + w + w 
combine like terms
32.6 = 7.8 + 8w
subtract 7.8 from both sides
24.8 = 8w
divide both sides by 8 to isolate w
3.1 = w

so we solved that the width is 3.1 cm
to find the length
l = 3.9 + (3*3.1)
l = 3.9 + 9.3
l = 13.2

The dimensions:
Length is 13.2 cm
Width is 3.1 cm

Hope this helps :)