The current going through the 4 Ω resistors is 2 A from the intensity shown on the figure. Thus the power absorbed is P = R*I2 so P = 4*(2) 2 = 16 W
Because of the two power supplies in the middle of the circuit, there is no current going through them, thus the only current trough the 6 Ω resistor is 2 A.
Thus the power absorbed is P = R*I2 so P = 6*(2) 2 = 24 W
For the 8 Ω resistor, the current going through it is I = U / R = 8 / 8 = 1A
Thus the power absorbed is P = R*I2 so P = 8*(1) 2 = 8 W