How do you solve 840 - 56

Welp ... 840-56 is um ... 784

840

56

{784}

•You borrow from the 4 changing it into a 3 putting 1 infront of the 0 changing into 10 so (10-6=4)

•now borrow again change 8 into 7 putting 1 infront of the 4 so (14-5=8)

•last drop the 7

Kinda hard to explain like this