Find closest multiple of $10$ to $12$. We see that $1 \times 10 = 10$ is the nearest. Now subtract $10$ from $12$ to get reminder $2$. Add $1$ to quotient.
Find closest multiple of $10$ to $21$. We see that $2 \times 10 = 20$ is the nearest. Now subtract $20$ from $21$ to get reminder $1$. Add $2$ to quotient.
Since $1$ is less than $10$, stop the division. The reminder is $1$. The topmost line $012$ is the quotient. Remove all zeros at the start of the quotient to get the actual quotient $12$.
