$\frac{ 13\left( x-6 \right)+12\left( x-4 \right) }{ 156 }$
Distribute $13$ through the parentheses$\frac{ 13x-78+12\left( x-4 \right) }{ 156 }$
Distribute $12$ through the parentheses$\frac{ 13x-78+12x-48 }{ 156 }$
Collect like terms$\frac{ 25x-78-48 }{ 156 }$
Calculate the difference$\frac{ 25x-126 }{ 156 }$