Alright, let's work through 9991 times 8936 step by step
9991 × 8936 = 8936 × (9991)
+ 8936 × 1 giving us 8936
+ 8936 × 90 what gives us 804240
+ 8936 × 900 yielding 8042400
+ 8936 × 9000 yielding 80424000

= 89279576
