Alright, let's work through 7991 times 6690 step by step
7991 × 6690 = 6690 × (7991)
+ 6690 × 1 that is equal 6690
+ 6690 × 90 giving us 602100
+ 6690 × 900 producing 6021000
+ 6690 × 7000 producing 46830000

= 53459790
