Alright, let's work through 9890 times 2391 step by step
9890 × 2391 = 2391 × (9890)
+ 2391 × 0 which equals 0
+ 2391 × 90 yielding 215190
+ 2391 × 800 that is equal 1912800
+ 2391 × 9000 giving us 21519000

= 23646990
