Alright, let's work through 3969 times 990 step by step
3969 × 990 = 990 × (3969)
+ 990 × 9 giving us 8910
+ 990 × 60 what gives us 59400
+ 990 × 900 which equals 891000
+ 990 × 3000 what gives us 2970000

= 3929310
