We see $f(x)$ appears inside of $g(x)$, which is $g(f(x))$
Therefore we can conclude that
$g(2x-3)=5-4(2x-3)$
since we plug in the input of the $g(x)$ function
now we solve the $2x-3=4$, so we get $2x=7, x=7/2$ then we plug in 7/2 into the $5-4(2x-3)$ expression,
this gives $5-4(7-3) = 5-4(4) = 4-16 = -12$
I get $\boxed{-12}$, however I suggest you check my work as I might have misunderstood, but this should give you an idea.
