Try multiplaying all sides
Answer:
32 cm
Step-by-step explanation:
As we could see if the image was a full rectangle with width is 7 cm and the length is 9 cm, the perimeter of it would be 32 cm.
Multiplying positive numbers always comes out positive, no matter how many there are. So you can forget about the positive ones.
Every two negative numbers in a multiplication produce a positive.
Another way to say that is: If the number of negative ones is EVEN,
the answer is positive, and if it's ODD, the answer is negative.
That monster product of eight numbers in problem #12 will be negative,
because there are an odd amount of negative factors in it.