By using calculus on $(1+x)^n$ and setting x equal to some appropriate number, evaluate the following

Question

$\sum_{r=0}^{n}{n \choose r} 2^r$

I've tried to get somewhere but I always get an r on the LHS of the equation and I'm not sure what to do with it

$(1+x)^n$$=$$\sum_{r=0}^{n}{n \choose r} x^r$

Then differentiate both sides with respect to x giving:

$n(1+x)^{n-1}$$=$$\sum_{r=0}^{n}{n \choose r} rx^{r-1}$

Multiply both sides by $x$ and then divide both sides by $r$ this gives:

$\frac{nx(1+x)^{n-1}}{r}$$=$$\sum_{r=0}^{n}{n \choose r} x^{r}$

Then set $x$ equal to $2$ but obviously I'm stuck with the r on the LHS of the equation then. What can I do?