Answer
$3_{four}$
Work Step by Step
$1$ is less than $2$, borrow one four from the next column
$(4+1)-2 =3_{ten}=3_{four}$
record the 3.
$\left[\begin{array}{lll}
& 2^{(*)} & 1_{four}\\
- & 1 & 2_{four}\\
- & - & -\\
& & 3_{four}
\end{array}\right]$
Next column:
we borrowed 1 from 2,
subtract $1-1=0_{ten}=0_{four}$
No need to record the 0,
Result = $3_{four}$
Check in base 10:
$9-6=3$
