The answer is b the second one
Firstly, expand the equation.

Next, move the variable x to the left and all the constant to the right.

Then, solve for x.
Remember that pi=180,
so 180/6=30, 30*5=150,
what's tan 150?
Remember that 150 degrees is in the 2nd quadrant, and this is tangent, so it means the answer must be negative, because tan 150= - tan 30, and -tan30=-√3/3.
Answer: -√3/3.