Question 975620
I'm assuming you mean the failures are independent.
a){{{P=0.8*0.9=0.72}}}
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b) {{{P=0.8*0.9+0.2*0.9+0.8*0.1=0.72+0.18+0.08=0.98}}}
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c) {{{P=0.2*0.9+0.8*0.1=0.26}}}