We look at the division of 12 by 90 
We're looking to find how many times 90 goes into 12.

Step 1:
When dividing 1 by 90, we get 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 90

On to step 2:
12 divided by 90 is 0 with a remainder of 12.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 12, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 3:
120 divided by 90 is 1 with a remainder of 30.
Use 1 as the next digit of our solution. 
Result so far: 0.1
Deduct 90 from 120 and we're left with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 4:
90 goes into 300 3 times with a remainder of 30.
The number 3 becomes the next digit in our result. 
Result so far: 0.13
Deduct 270 from 300 and we're left with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Moving on to step 5:
When dividing 300 by 90, we get 3 with a remainder of 30.
The number 3 becomes the next digit in our result. 
Result so far: 0.133
The remainder is 30 after subtracting 270 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Our division results in 0.133 with a remaining 0.003.