Writing to explain use rounding to estimate the product 12×9. then, use compensation to find the total cost for 12 books that were $9 each, would she get a good estimate? explain

So if we do not know what 12 times 9 is then we can round 9 to 10 and get
12 times 10
most people can multiply by ten so this should be easy so
12 times 10=120

12 times 9=108
she was off by 12 so a 10% deviation error

another way to do it is you multiply 12 by 10 and get 10 12's
then you subtract 1  12 and get 9  12's

What type of problem do you need with?