12866 ÷ 9 = 1429 R5
Let's divide 12866 by 9.

Step 1:
9 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 1 to get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 9

Step 2:
9 goes into 12 1 times with a remainder of 3.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 9 from 12 to get 3.
Bring next digit (8) of the dividend behind the 3 and repeat the process: 38 / 9

Step 3:
9 goes into 38 4 times with a remainder of 2.
Write down 4 as next digit of of the result. 
Result so far: 14
Subtract 36 from 38 to get 2.
Bring next digit (6) of the dividend behind the 2 and repeat the process: 26 / 9

Step 4:
9 goes into 26 2 times with a remainder of 8.
Write down 2 as next digit of of the result. 
Result so far: 142
Subtract 18 from 26 to get 8.
Bring next digit (6) of the dividend behind the 8 and repeat the process: 86 / 9

Step 5:
9 goes into 86 9 times with a remainder of 5.
Write down 9 as next digit of of the result. 
Result so far: 1429
Subtract 81 from 86 to get 5.

The final result is 1429 with a remainder of 5.