How to find the complex power for a current source?
Here's how I might approach this problem:

Use superposition to write

$$V_x = 5\angle30\cdot j||(2 - j) + 2V_x \cdot \frac{2}{j - j + 2} \cdot j $$

Gather terms

$$V_x (1 - j2) =  5\angle30\cdot j||(2 - j)  $$

Isolate the desired variable

$$V_x = 5\angle30\frac{j||(2 - j)}{(1 - 2j)}$$

Since the complex power delivered is

$$S = V_x \cdot 5\angle{-30}$$

See that

$$S = 25\frac{j||(2 - j)}{(1 - 2j)} = (-7.5 + j10)VA$$