For the given functions $f$ and $g,$ complete parts $($a$)-($h$).$ For parts $($a$)-($d$),$ also find the domain.

$f(x)=\frac{4x+7}{7x-4}$;$g(x)=\frac{7x}{7x-4}$

$($a$)$ Find $(f+g)(x).$

$(f+g)(x)=,(Simplify$ your answer. $)$