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I first found the current, using P=IV. But here is the total power 30W+40W=70W? Then I did:70W=I*120V, I=7/12, then I found Resistance by using R=P/I^2, R=30W/(7/12)^2=88ohms. But somehow the answer seems to be wrong. Its resistance is smaller than the resistance in a parallel circuit, and it's impossible. Hope you can point out my mistake. Thanks.