Solve for: 107-29

Expression: $107-29$

In the bolded column, subtract the second digit from the first

$\begin{matrix}\:\:&1&0&\bold{7}\\-&0&2&\bold{9}\end{matrix}$

The top digit is not bigger than the bottom one. Try to 'borrow' a digit from the left.

$\begin{matrix}\:\:&1&\bold{0}&7\\-&0&\bold{2}&9\end{matrix}$

Borrow $1$ from $1$. The remainder is $0$

$\begin{matrix}\:\:&\bold{0}&10&\:\:\\\:\:&\bold{\linethrough{1}}&0&7\\-&\bold{0}&2&9\end{matrix}$

Add $1$ ten to $010+0=10$

$\begin{matrix}\:\:&0&\bold{10}&\:\:\\\:\:&\linethrough{1}&\bold{\linethrough{0}}&7\\-&0&\bold{2}&9\end{matrix}$

Borrow $1$ from $10$. The remainder is $9$

$\begin{matrix}\:\:&0&\bold{9}&10\\\:\:&\linethrough{1}&\bold{\linethrough{10}}&7\\-&0&\bold{2}&9\end{matrix}$

Add $1$ ten to $710+7=17$

$\begin{matrix}\:\:&0&9&\bold{17}\\\:\:&\linethrough{1}&\linethrough{10}&\bold{\linethrough{7}}\\-&0&2&\bold{9}\end{matrix}$

In the bolded column, subtract the second digit from the first $17-9=8$

$\frac{\begin{matrix}\:\:&0&9&\bold{17}\\\:\:&\linethrough{1}&\linethrough{10}&\bold{\linethrough{7}}\\-&0&2&\bold{9}\end{matrix}}{\begin{matrix}\:\:&\:\:&\:\:&\bold{8}\end{matrix}}$

In the bolded column, subtract the second digit from the first $9-2=7$

$\frac{\begin{matrix}\:\:&0&\bold{9}&17\\\:\:&\linethrough{1}&\bold{\linethrough{10}}&\linethrough{7}\\-&0&\bold{2}&9\end{matrix}}{\begin{matrix}\:\:&\:\:&\bold{7}&8\end{matrix}}$

In the bolded column, subtract the second digit from the first $0-0=0$

$\frac{\begin{matrix}\:\:&\bold{0}&9&17\\\:\:&\bold{\linethrough{1}}&\linethrough{10}&\linethrough{7}\\-&\bold{0}&2&9\end{matrix}}{\begin{matrix}\:\:&\bold{0}&7&8\end{matrix}}$

Line up the numbers

$\begin{matrix}\:\:&1&0&7\\-&0&2&9\end{matrix}$ $=78$