Answer:
3 cm by 6 cm
Step-by-step explanation:
Represent the length and width by L and W.
The perimeter is P = 2L + 2W, and here the perimeter is 18 cm.
Finally, L = W + 3 cm. substituting W + 3 cm for L in the above equation, we get:
18 cm = 2(W + 3) + 2W, or (after reduction)
9 cm = W + 3 cm + W
Then 2W = 6 cm, or W = 3 cm.
Then the length is L = W + 3, or 3 cm + 3cm = 6 cm
The dimensions of the rectangle are 3 cm by 6 cm.
Check: Does 2(3 cm) + 2(6 cm) = 18 cm? Yes