I WILL GIVE DISLIKES $!!!$ IF ANYTHING WRONG HAPPENS IN MY QUESTION, BETTER SKIP IT$!!!$

$\mathrm{.}6.()$ X UY $=$ X $$ XI $$ Y $=0$ t give solution $$ Y $=$ UDon't Solve $78$ AUB $=$ An Biff A $=$ B $9$Don VD$14\text{'}$t $()(-)=0(6)$ AU$($B $-$ A$)=$ AUB $($C$)($AUB$)-$ C $=($A $-$C$)$ U $($B$-$C$)()($A $-$ B$)$ U $($B $-$ A$)=($AUB$)-()()($A $-$ B $-$ C $=($A $-$C$)-($B$-$C$)$ : $($a$)$ A CB iff AnB $=0$ A$,$ B$,$ C $$