Alright, let's work through 2640 times 7145 step by step
2640 × 7145 = 7145 × (2640)
+ 7145 × 0 which equals 0
+ 7145 × 40 yielding 285800
+ 7145 × 600 which equals 4287000
+ 7145 × 2000 that equals 14290000

= 18862800
