Find closest multiple of $12$ to $43$. We see that $3 \times 12 = 36$ is the nearest. Now subtract $36$ from $43$ to get reminder $7$. Add $3$ to quotient.
Since $7$ is less than $12$, stop the division. The reminder is $7$. The topmost line $03$ is the quotient. Remove all zeros at the start of the quotient to get the actual quotient $3$.