Question Number 1132 by 123456 last updated on 24/Jun/15
$$\mathrm{let}\:\mathrm{S}=\left\{\mathrm{1},\mathrm{2},\mathrm{3},\mathrm{4},\mathrm{5}\right\},\:\mathrm{if}\:\mathrm{A},\mathrm{B},\mathrm{C}\:\mathrm{is}\:\mathrm{such}\:\mathrm{that} \\ $$$$\mathrm{A}\cap\mathrm{B}\cap\mathrm{C}=\varnothing \\ $$$$\mathrm{A}\cap\mathrm{B}\neq\varnothing \\ $$$$\mathrm{A}\cap\mathrm{C}\neq\varnothing \\ $$$$\mathrm{how}\:\mathrm{many}\:\mathrm{ways}\:\mathrm{can}\:\mathrm{be}\:\mathrm{choose}\:\mathrm{A},\mathrm{B}\:\mathrm{and} \\ $$$$\mathrm{C} \\ $$
Commented by Faaiz Soomro last updated on 14/Jul/15
$${When}\:{I}\:{see}\:{this}\:{problem}\:{in}\:{the}\:{list}\:{there}\:{is}\:{written} \\ $$$${A}\cap{B}=\phi \\ $$$${A}\cap{C}=\phi \\ $$$${but}\:{now}\:{when}\:{I}\:{am}\:{commenting}\:{there}\:{is}\:{written}\:{unequal} \\ $$$${instead}\:{of}\:=\:{sign}.{What}\:{is}\:{the}\:{problem}?\:{Pl}\:{try}\:{to}\:{write}\:{a} \\ $$$${comment}\:{and}\:{note}\:{this}.{What}\:{is}\:{correct}? \\ $$$${I}\:{think}\:{this}\:{problem}\:{is}\:{in}\:{my}\:{tablet}. \\ $$