Answer:
[tex]\large\boxed{\left\{\begin{array}{ccc}y-17z=-15&(a)\\-2y+17z=13&(b)\end{array}\right}[/tex]
Step-by-step explanation:
[tex]\left\{\begin{array}{ccc}2x-3y+5z=5&(1)\\4x-5y-7z=-5&(2)\\-6x+7y+2z=-2&(3)\end{array}\right\\\\\\\text{From (1) and (2)}\\\left\{\begin{array}{ccc}2x-3y+5z=5&(1)&\text{multiply both sides by (-2)}\\4x-5y-7z=-5&(2)\end{array}\right\\\underline{+\left\{\begin{array}{ccc}-4x+6y-10z=-10\\4x-5y-7z=-5\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad y-17z=-15\qquad(a)[/tex]
[tex]\text{From (1) and (3)}\\\left\{\begin{array}{ccc}2x-3y+5z=5&(1)&\text{multiply both sides by 3}\\-6x+7y+2z=-2&(3)\end{array}\right\\\underline{+\left\{\begin{array}{ccc}6x-9y+15z=15\\-6x+7y+2z=-2\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad\qquad-2y+17z=13\qquad(b)[/tex]
