Alright, let's work through 9991 times 7867 step by step
9991 × 7867 = 7867 × (9991)
+ 7867 × 1 producing 7867
+ 7867 × 90 yielding 708030
+ 7867 × 900 that results in 7080300
+ 7867 × 9000 which equals 70803000

= 78599197
