Alright, let's work through 7931 times 3855 step by step
7931 × 3855 = 3855 × (7931)
+ 3855 × 1 producing 3855
+ 3855 × 30 producing 115650
+ 3855 × 900 that equals 3469500
+ 3855 × 7000 giving us 26985000

= 30574005
