Answer:
width:9
length: 12
Explanation:
width: substitute for x
length: since the length is 3 cm greater than the width, we substitute it for x+3.
we know that you need to add all the lengths to find the perimeter, and we know that the perimeter of the rectangle is 42 cm, so our equation is formed.
x+x+x+3+x+3=42
4x+6=42
4x=36
x=9
width:9
length:9+3=12