51965 ÷ 3 = 17321 R2
Let's divide 51965 by 3.

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

Step 2:
3 goes into 21 7 times with a remainder of 0.
Write down 7 as next digit of of the result. 
Result so far: 17
Subtract 21 from 21 to get 0.
Bring next digit (9) of the dividend behind the 0 and repeat the process: 9 / 3

Step 3:
3 goes into 9 3 times with a remainder of 0.
Write down 3 as next digit of of the result. 
Result so far: 173
Subtract 9 from 9 to get 0.
Bring next digit (6) of the dividend behind the 0 and repeat the process: 6 / 3

Step 4:
3 goes into 6 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 1732
Subtract 6 from 6 to get 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 3

Step 5:
3 goes into 5 1 times with a remainder of 2.
Write down 1 as next digit of of the result. 
Result so far: 17321
Subtract 3 from 5 to get 2.

The final result is 17321 with a remainder of 2.