$23-18=23-18=$

Subtract from right to left. First, subtract the ones digit. Since $33$ is smaller than $88$, you need to calculate $13-8=513-8=\; 5$ instead and "memorize" a 1 at the tens digit.

$\begin{array}{c}23\\ \underset{‾}{-1_{1}8}\\ 5\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;2\backslash ;\backslash ;\backslash hspace\{1mm\}3\backslash ;\backslash \backslash \backslash underline\{-\backslash ;1\_1\backslash ;8\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;5\backslash end\{array\}$

Now subtract the tens: $2-(1+1)=02-(1+1)=0$

The result is therefore $55$.

$45-29=45-29=$

$\begin{array}{c}45\\ \underset{‾}{-2_{1}9}\\ 6\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;4\backslash ;5\backslash ;\backslash \backslash \backslash underline\{-\backslash ;\backslash ;2\_1\backslash ;9\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash hspace\{1mm\}\backslash ;\backslash ;\backslash ;6\backslash end\{array\}$

Subtract from right to left. First, subtract the ones digit. Since $99$ is larger than $55$ you need to calculate $15-9=615-9=6$ instead and "memorize" a 1 at the tens digit.

$\begin{array}{c}45\\ \underset{‾}{-2_{1}9}\\ 16\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;4\backslash ;5\backslash ;\backslash \backslash \backslash underline\{-\backslash ;2\_1\backslash ;9\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash hspace\{1mm\}\backslash ;1\backslash ;6\backslash end\{array\}$

Now subtract the tens: $4-(2+1)=14-(2+1)=1$.

The result is therefore $1616$.

$14-10=14-10=$

Calculate from right to left. Subtract the ones first: $4-0=44-0=4$.

$\begin{array}{c}14\\ \underset{‾}{-10}\\ 4\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;1\backslash ;4\backslash ;\backslash \backslash \backslash underline\{-\backslash ;1\backslash ;0\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;4\backslash end\{array\}$

Now subtract the tens: $1-1=01-1=0$.

The result is therefore $44$.

$19-15=19-15=$

Subtract from left to right. Subtract the ones first: $9-5=49-5=4$.

$\begin{array}{c}19\\ \underset{‾}{-15}\\ 4\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;1\backslash ;9\backslash ;\backslash \backslash \backslash underline\{-\backslash ;1\backslash ;5\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;4\backslash end\{array\}$

Now subtract the tens: $1-1=01-1=0$.

The result is therefore $44$.

$57-46=57-46=$

Subtract from left to right. Subtract the ones first: $7-6=17-6=1$.

$\begin{array}{c}57\\ \underset{‾}{-46}\\ 1\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;5\backslash ;7\backslash ;\backslash \backslash \backslash underline\{-\backslash ;4\backslash ;6\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;\backslash ;1\backslash end\{array\}$

Now subtract the tens: $5-4=15-4=1$.

$\begin{array}{c}57\\ \underset{‾}{-46}\\ 11\end{array}\backslash def\backslash arraystretch\{1.25\}\; \backslash begin\{array\}\{l\}\backslash ;\backslash ;\backslash ;\backslash ;5\backslash ;7\backslash ;\backslash \backslash \backslash underline\{-\backslash ;4\backslash ;6\}\backslash \backslash \backslash ;\backslash ;\backslash ;\backslash ;1\backslash ;1\backslash end\{array\}$

The result is therefore $1111$.