Let's plug the value:
[tex]f(x)=2^x \implies f(\log_2(5))=2^{\log_2(5)}[/tex]
Recall that exponent and logarithm are inverse operations:
[tex]a^{\log_a(b)}=b[/tex]
So, we have
[tex]2^{\log_2(5)}=5[/tex]
