We're dividing 138971 by 42 
Our goal is to divide 138971 by 42.

Moving on to step 1:
1 divided by 42 is 0 with a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Fetch the next digit (3) from the dividend, attach it to 1 and continue: 13 / 42

On to step 2:
13 divided by 42 is 0 with a remainder of 13.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 13, we end up with 13.
Fetch the next digit (8) from the dividend, attach it to 13 and continue: 138 / 42

On to step 3:
138 divided by 42 is 3 with a remainder of 12.
The next digit of our result is 3. 
Result so far: 3.0
Deduct 126 from 138 and we're left with 12.
Bring next digit (9) of the dividend behind the 12 and repeat the process: 129 / 42

Advancing to step 4:
When dividing 129 by 42, we get 3 with a remainder of 3.
Record the quotient 3 as the next digit in the result. 
Result so far: 33.0
Subtract 126 from 129 to get 3.
Fetch the next digit (7) from the dividend, attach it to 3 and continue: 37 / 42

Moving on to step 5:
42 can be fit into 37 0 times, resulting in a remainder of 37.
Write down 0 as next digit of the result. 
Result so far: 330.0
Subtracting 0 from 37 leaves us with 37.
Include the next digit (1) from the dividend after 37, then repeat: 371 / 42

Moving on to step 6:
When dividing 371 by 42, we get 8 with a remainder of 35.
Use 8 as the next digit of our solution. 
Result so far: 3308.0
If we take 336 away from 371, we end up with 35.
Since there are no more digits in the dividend, we add a zero to the remainder making it 350, and continue the process.

Let's proceed to step 7:
42 can be fit into 350 8 times, resulting in a remainder of 14.
The next digit of our result is 8. 
Result so far: 3308.8
Subtracting 336 from 350 leaves us 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.

Advancing to step 8:
140 divided by 42 is 3 with a remainder of 14.
Use 3 as the next digit of our solution. 
Result so far: 3308.83
Subtract 126 from 140 to get 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 9:
140 divided by 42 is 3 with a remainder of 14.
The number 3 becomes the next digit in our result. 
Result so far: 3308.833
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.

After the division, we end up with 3308.833 and a remainder of 0.0014.