12120 ÷ 7 = 1731 R3
We're going to perform division on 12120 with 7 as the divisor.

Step 1:
7 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 / 7

Step 2:
7 goes into 12 1 times with a remainder of 5.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 7 from 12 to get 5.
Bring next digit (1) of the dividend behind the 5 and repeat the process: 51 / 7

Step 3:
7 goes into 51 7 times with a remainder of 2.
Write down 7 as next digit of of the result. 
Result so far: 17
Subtract 49 from 51 to get 2.
Bring next digit (2) of the dividend behind the 2 and repeat the process: 22 / 7

Step 4:
7 goes into 22 3 times with a remainder of 1.
Write down 3 as next digit of of the result. 
Result so far: 173
Subtract 21 from 22 to get 1.
Bring next digit (0) of the dividend behind the 1 and repeat the process: 10 / 7

Step 5:
7 goes into 10 1 times with a remainder of 3.
Write down 1 as next digit of of the result. 
Result so far: 1731
Subtract 7 from 10 to get 3.

The final result is 1731 with a remainder of 3.