42051 ÷ 3 = 14017 R0
We're going to perform division on 42051 with 3 as the divisor.

Step 1:
3 goes into 4 1 times with a remainder of 1.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 3 from 4 to get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 3

Step 2:
3 goes into 12 4 times with a remainder of 0.
Write down 4 as next digit of of the result. 
Result so far: 14
Subtract 12 from 12 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 3

Step 3:
3 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 140
Subtract 0 from 0 to get 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 3

Step 4:
3 goes into 5 1 times with a remainder of 2.
Write down 1 as next digit of of the result. 
Result so far: 1401
Subtract 3 from 5 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 3

Step 5:
3 goes into 21 7 times with a remainder of 0.
Write down 7 as next digit of of the result. 
Result so far: 14017
Subtract 21 from 21 to get 0.

The final result is 14017 with a remainder of 0.