$\left( 9+3 \right)+\left( \frac{ 3 }{ 5 }+\frac{ 4 }{ 7 } \right)$
Add the numbers$12+\left( \frac{ 3 }{ 5 }+\frac{ 4 }{ 7 } \right)$
Add the fractions$12+\frac{ 41 }{ 35 }$
Convert the improper fraction into a mixed number$12+1 \frac{ 6 }{ 35 }$
Write the mixed number as a sum of the whole number and the fractional part$12+1+\frac{ 6 }{ 35 }$
Add the numbers$13+\frac{ 6 }{ 35 }$
Write the sum of the whole number and the fraction as a mixed number$\begin{align*}&13 \frac{ 6 }{ 35 } \\&\begin{array} { l }\frac{ 461 }{ 35 },& 13.1\overset{ \cdot }{ 7 } 1428\overset{ \cdot }{ 5 } \end{array}\end{align*}$