Question 304579
l = length  w = width

Let's write what we know

l = w + 12  ....one side is 12 cm longer that the other
2l + 2w = 44 ....since you add up all sides for the perimeter and there are 2 lengths and 2 widths

now use substitution since we know l = w + 12
2(w + 12) + 2w =44
2w + 24 + 2w = 44
4w + 24 = 44  subtract 24 from both sides
4w = 20  divide by 4
w = 5  

now that you know what w is: 
l = 5 + 12  (first equation)
l = 17  so now you know

w = 5cm and l = 17cm