Find the power dissipated by the controller source
The controlling source is \$ V_o \$ and the controlled source is \$ 2 \cdot V_o \$ as shown by the diamond symbol.

Step 1 is to find I which we calculating by noting.

\$ V_o = I \cdot 4 \Omega \$ and \$ I = -(10A + 2S \cdot (4 \Omega \cdot I)) = -(10A + 8 \cdot I) \$

Solve this for \$ I \$ and we can calculate both the current in the controlled source and the voltage across it.  From there we can calculate power dissipation.

The power dissipation in the the controlling source is simply \$ I^2 \cdot R \$

Note: since voltage and current are fundamentally different quantities we need to to know the scaling factor. I am assuming 1 amp per volt i.e \$ S \$.