Alright, let's work through 9129 times 9901 step by step
9129 × 9901 = 9901 × (9129)
+ 9901 × 9 that results in 89109
+ 9901 × 20 that results in 198020
+ 9901 × 100 giving us 990100
+ 9901 × 9000 giving us 89109000

= 90386229
