Hi!
To get a good estimate you would round 47% up to 50% and 89 up to 90. Since 50% is half, making one of your answers divide 90 by 2.
You can also round 47% to 50% and make it into a decimal, so .5. This means you can also multiply .5 by 90.
Lastly, you can round 47% to 50% and make it a fraction, which would be 1/2. Therefore, you can multiple 1/2 by 90 and get the same answer.
Overall, the correct answers should be A, B, and D.
Hope this helps!