Alright, let's work through 1978 times 7815 step by step
1978 × 7815 = 7815 × (1978)
+ 7815 × 8 that is equal 62520
+ 7815 × 70 resulting in 547050
+ 7815 × 900 yielding 7033500
+ 7815 × 1000 which equals 7815000

= 15458070
