$\left ( \color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ + } \color{#FF6800}{ 1 } \right ) \color{#FF6800}{ - } \left ( \color{#FF6800}{ - } \color{#FF6800}{ 3 } \color{#FF6800}{ a } \color{#FF6800}{ - } \color{#FF6800}{ 5 } \right )$
$ $ Get rid of unnecessary parentheses $ $
$\color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ + } \color{#FF6800}{ 1 } \color{#FF6800}{ - } \left ( \color{#FF6800}{ - } \color{#FF6800}{ 3 } \color{#FF6800}{ a } \color{#FF6800}{ - } \color{#FF6800}{ 5 } \right )$
$2 a + 1 \color{#FF6800}{ - } \left ( \color{#FF6800}{ - } \color{#FF6800}{ 3 } \color{#FF6800}{ a } \color{#FF6800}{ - } \color{#FF6800}{ 5 } \right )$
$ $ Change the symbol of each term in parentheses when there is a (-) symbol in front of parentheses $ $
$2 a + 1 + \color{#FF6800}{ 3 } \color{#FF6800}{ a } + \color{#FF6800}{ 5 }$
$\color{#FF6800}{ 2 } \color{#FF6800}{ a } \color{#FF6800}{ + } \color{#FF6800}{ 1 } \color{#FF6800}{ + } \color{#FF6800}{ 3 } \color{#FF6800}{ a } \color{#FF6800}{ + } \color{#FF6800}{ 5 }$
$ $ Organize the similar terms $ $
$\left ( \color{#FF6800}{ 2 } \color{#FF6800}{ + } \color{#FF6800}{ 3 } \right ) \color{#FF6800}{ a } \color{#FF6800}{ + } \left ( \color{#FF6800}{ 1 } \color{#FF6800}{ + } \color{#FF6800}{ 5 } \right )$
$\left ( \color{#FF6800}{ 2 } \color{#FF6800}{ + } \color{#FF6800}{ 3 } \right ) \color{#FF6800}{ a } + \left ( 1 + 5 \right )$
$ $ Arrange the constant term $ $
$\color{#FF6800}{ 5 } \color{#FF6800}{ a } + \left ( 1 + 5 \right )$
$5 a + \left ( \color{#FF6800}{ 1 } \color{#FF6800}{ + } \color{#FF6800}{ 5 } \right )$
$ $ Arrange the constant term $ $
$5 a + \color{#FF6800}{ 6 }$