Show that the equation
$$\sin \left( x + 30 ^ { \circ } \right) = 2 \cos \left( x + 60 ^ { \circ } \right)$$
can be written in the form
$$( 3 \sqrt { } 3 ) \sin x = \cos x$$
Hence solve the equation
$$\sin \left( x + 30 ^ { \circ } \right) = 2 \cos \left( x + 60 ^ { \circ } \right)$$
for \(- 180 ^ { \circ } \leqslant x \leqslant 180 ^ { \circ }\).