We're dividing 77840 by 21 
We want to divide 77840 by 21.

Advancing to step 1:
21 goes into 7 0 times with a remainder of 7.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 7 after subtracting 0 from 7.
Bring next digit (7) of the dividend behind the 7 and repeat the process: 77 / 21

Step 2:
21 goes into 77 3 times with a remainder of 14.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 63 from 77 and we're left with 14.
Take the next digit (8) from the dividend and append it to 14, then repeat: 148 / 21

Moving on to step 3:
21 can be fit into 148 7 times, resulting in a remainder of 1.
Put 7 as the next digit of the answer. 
Result so far: 37.0
The remainder is 1 after subtracting 147 from 148.
Bring next digit (4) of the dividend behind the 1 and repeat the process: 14 / 21

Moving on to step 4:
21 goes into 14 0 times with a remainder of 14.
Write down 0 as next digit of the result. 
Result so far: 370.0
Deduct 0 from 14 and we're left with 14.
Bring next digit (0) of the dividend behind the 14 and repeat the process: 140 / 21

Advancing to step 5:
If we divide 140 by 21, we get 6 and a remainder of 14.
Record the quotient 6 as the next digit in the result. 
Result so far: 3706.0
If we take 126 away from 140, we end up with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Step 6:
21 can be fit into 140 6 times, resulting in a remainder of 14.
Use 6 as the next digit of our solution. 
Result so far: 3706.6
If we take 126 away from 140, we end up with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Moving on to step 7:
When dividing 140 by 21, we get 6 with a remainder of 14.
The number 6 becomes the next digit in our result. 
Result so far: 3706.66
Deduct 126 from 140 and we're left with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

The final outcome is 3706.66, with a leftover of 0.014.