calculus - Numerical approximation by hand of arctan?

Is there any numerical method I can use by hand to solve an equation with $\arctan$?

I have for instance:

$$2x\frac{180^\circ}{\pi}+\arctan(2x)=150^\circ$$
Or in radians:

$$2x+\arctan(2x)=\frac{5\pi}{6}$$

Update:

With "by hand" I mean without a computer, just with pen, paper and a simple calculator.