80 is closer to 100 than to 0 so you add 100 to 9000 which gives you 9100.
It is then 90.7 when rounded up to the nearest tenth
9080 to the nearest hundreds is 9100
round 90 to the nearest ten
372 rounded to the nearest hundred is 400
300
100
100
100
2,222 rounded to the nearest 100 is 2,200.
10100
100
4198 to the nearest 100 = 4200