$- \dfrac { 3 } { \color{#FF6800}{ 4 } } + \dfrac { 5 } { \color{#FF6800}{ 12 } }$
$ $ The smallest common multiple in denominator is $ 12$
$- \dfrac { 3 } { \color{#FF6800}{ 4 } } + \dfrac { 5 } { \color{#FF6800}{ 12 } }$
$- \dfrac { 3 } { 4 } + \dfrac { 5 } { 12 }$
$ $ Multiply the denominator and the numerator so that the denominator is the smallest common multiple $ $
$- \dfrac { 3 \times \color{#FF6800}{ 3 } } { 4 \times \color{#FF6800}{ 3 } } + \dfrac { 5 } { 12 }$
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 3 \times 3 } { 4 \times 3 } } \color{#FF6800}{ + } \color{#FF6800}{ \dfrac { 5 } { 12 } }$
$ $ Organize the expression $ $
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 9 } { 12 } } \color{#FF6800}{ + } \color{#FF6800}{ \dfrac { 5 } { 12 } }$
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 9 } { 12 } } \color{#FF6800}{ + } \color{#FF6800}{ \dfrac { 5 } { 12 } }$
$ $ Since the denominator is the same as $ 12 $ , combine the fractions into one $ $
$\color{#FF6800}{ \dfrac { - 9 + 5 } { 12 } }$
$\dfrac { \color{#FF6800}{ - } \color{#FF6800}{ 9 } \color{#FF6800}{ + } \color{#FF6800}{ 5 } } { 12 }$
$ $ Add $ - 9 $ and $ 5$
$\dfrac { \color{#FF6800}{ - } \color{#FF6800}{ 4 } } { 12 }$
$\dfrac { \color{#FF6800}{ - } \color{#FF6800}{ 4 } } { 12 }$
$ $ Move the minus sign to the front of the fraction $ $
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 4 } { 12 } }$
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 4 } { 12 } }$
$ $ Reduce the fraction to the lowest term $ $
$\color{#FF6800}{ - } \color{#FF6800}{ \dfrac { 1 } { 3 } }$