Hello,
1)
[tex]\left\{\begin{array}{ccc}2x-y&=&7\\-2x+3y&=&9\\\end{array} \right.\\\\\\\left\{\begin{array}{ccc}2y&=&16\\-2x+3y&=&9\\\end{array} \right.\\\\\\\left\{\begin{array}{ccc}y&=&8\\-2x+3*8&=&9\\\end{array} \right.\\\\\\\left\{\begin{array}{ccc}x&=&7.5\\y&=&8\\\end{array} \right.\\\\[/tex]
Answer C
2)
[tex]\left\{\begin{array}{ccc}x-2y-3z&=&5\\x+2y+3z&=&7\\x+z&=&3\\\end{array} \right.\\\\\\\left\{\begin{array}{ccc}2x&=&12\\x+2y+3z&=&7\\x+z&=&3\\\end{array} \right.\\\\\\\left\{\begin{array}{ccc}x&=&6\\2y+3z&=&1\\z&=&-3\\\end{array} \right.\\\\\\\\\left\{\begin{array}{ccc}x&=&6\\y&=&5\\z&=&-3\\\end{array} \right.\\\\\\[/tex]
Answer C
