How much power is dissipated by each resistor in the figure

..in which V = 24 V and R2 = 18 ?

resistor 1____W
resistor 2____W



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The total resistance is
R = 12 Ohm + 18 Ohm = 30 Ohm.
Hence the total current in th circuit is

I = V/R = 24 V / 30 Ohm = 0.80 A

The power dissipated in the resistors is (rounded to two significant digits)

P1 = I^2 R = (0.80 A)^2 * 12 Ohm = 7.7 W

P2 = I^2 R = (0.80 A)^2 * 18 Ohm = 12 W

total (series) resistance is the sum, 30 ohms. then by Ohm's law you deduce that I = U/R = 24V/30ohm = 0.8A.
P = U*I = I^2*R = 0.8A^2 * 12ohm = 7.68W for R1 and P = I^2 * 18ohm = 11.52W for R2.

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