Nvm, I simplified it too quickly.
\frac{1}{2}\pi r^2 = \pi r + 2r
\pi r^2 = 2\pi r + 4r
\pi r^2 = 2\pi r + 4r
Now divide the equation on RHS by \pi r, and you get:
r = 2 + \frac{4}{\pi}
Combine fractions.
r = \frac{2 \pi + 4}{\pi}
Ignore mine, to type it out, it's pretty much the same...