r⋅a=9 ⇒‌‌2x+3y+z=9.....(i) ⇒r⋅b=7 ⇒4x+y=7....(ii) ⇒‌‌r⋅c=6 ⇒‌‌x−3y−7z=6.....(iii) On adding Eqs. (i) and (iii), we get ⇒‌3x−6z=15 ⇒‌x−2z=5⇒2z=x−5 ⇒‌z=‌
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(x−5) From Eq. (ii), we get y=7−4x put z=‌
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(x−5) and y=7−4x in Eq. (i) ‌2x+3y+z=9 ⇒2x+3(7−4x)+‌
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(x−5)=9 ⇒4x+42−24x+x−5=18 ⇒−19x+19=0⇒x=1,y=7−4=3 ‌ and ‌‌z=‌