$\dfrac { 3 } { 4 } \color{#FF6800}{ \times } \color{#FF6800}{ 12 }$
$ $ Natural numbers can be expressed as fractions with a denominator of 1 $ $
$\dfrac { 3 } { 4 } \color{#FF6800}{ \times } \color{#FF6800}{ \dfrac { \color{#FF6800}{ 12 } } { \color{#FF6800}{ 1 } } }$
$\dfrac { 3 } { \color{#FF6800}{ 4 } } \times \dfrac { \color{#FF6800}{ 12 } } { 1 }$
$ $ Reduce all denominators and numerators that can be reduced $ $
$\dfrac { 3 } { \color{#FF6800}{ 1 } } \times \dfrac { \color{#FF6800}{ 3 } } { 1 }$
$\color{#FF6800}{ \dfrac { \color{#FF6800}{ 3 } } { \color{#FF6800}{ 1 } } } \color{#FF6800}{ \times } \color{#FF6800}{ \dfrac { \color{#FF6800}{ 3 } } { \color{#FF6800}{ 1 } } }$
$ $ numerator multiply between numerator, and denominators multiply between denominators $ $
$\color{#FF6800}{ \dfrac { \color{#FF6800}{ 3 } \color{#FF6800}{ \times } \color{#FF6800}{ 3 } } { \color{#FF6800}{ 1 } \color{#FF6800}{ \times } \color{#FF6800}{ 1 } } }$
$\dfrac { \color{#FF6800}{ 3 } \color{#FF6800}{ \times } \color{#FF6800}{ 3 } } { 1 \times 1 }$
$ $ Multiply $ 3 $ and $ 3$
$\dfrac { \color{#FF6800}{ 9 } } { 1 \times 1 }$
$\dfrac { 9 } { \color{#FF6800}{ 1 } \times 1 }$
$ $ Multiplying any number by 1 does not change the value $ $
$\dfrac { 9 } { \color{#FF6800}{ 1 } }$
$\dfrac { 9 } { \color{#FF6800}{ 1 } }$
$ $ If the denominator is 1, the denominator can be removed $ $
$\color{#FF6800}{ 9 }$