Answers:
900 goes in the green box
7200 goes in the gray box
Explanation
The 891 has 8 in the hundreds place value. Just to the right of it is 9, which fits the "5 or more" criteria. This means we bump that 8 up to 9, then replace everything else with 0s.
Therefore 891 rounds to 900 when rounding to the nearest hundred. Notice that 891 is closer to 900 than it is to 800. It might help to draw out a number line.
Then 900 x 8 = 7200 since 9 x 8 = 72 and we tack on those extra zeros at the end.
