Alright, let's work through 1991 times 5878 step by step
1991 × 5878 = 5878 × (1991)
+ 5878 × 1 that equals 5878
+ 5878 × 90 which equals 529020
+ 5878 × 900 which equals 5290200
+ 5878 × 1000 that results in 5878000

= 11703098
