Alright, let's work through 3791 times 21 step by step
3791 × 21 = 21 × (3791)
+ 21 × 1 what gives us 21
+ 21 × 90 that is equal 1890
+ 21 × 700 that equals 14700
+ 21 × 3000 which equals 63000

= 79611
