Alright, let's work through 8458 times 780 step by step
8458 × 780 = 780 × (8458)
+ 780 × 8 giving us 6240
+ 780 × 50 that is equal 39000
+ 780 × 400 giving us 312000
+ 780 × 8000 yielding 6240000

= 6597240
