Quick Notes

Mathematical sentence: \(7\space\text{hours}\space+\space6\space\text{hours}\space-\space4\space\text{hours}\space=\underline{\quad\quad}\,\text{hours}\)

METHOD

 \(\begin{array} {rr} \\\space7\;\;\text{hours} \\+\;\;\;\space6\;\;\text{hours} \\\hline\;\;\;1\;3\;\;\text{hours}\\\hline \end{array}\)    \(\Longrightarrow\)      \(\begin{array} {rr} \\\;1\;3\;\;\text{hours} \\-\;\;\;\space4\;\;\text{hours} \\\hline\;\;\;\;9\;\;\text{hours}\\\hline \end{array}\)