Question 210102
Are you sure that the answer provided is (6,1,7)? If this is what the book is telling you, then it is wrong. Why? The ordered triple (6,1,7) means that {{{x=6}}}, {{{y=1}}} and {{{z=7}}}. These values must satisfy all three equations. 



However, if we pick the second equation and plug in the given values, we get:


{{{6+2(1)=-5}}}


{{{6+2=-5}}}


{{{8=-5}}}


which is clearly NOT true. So either the book has the wrong answer, or there's a typo in the problem. Either way, I'd double check everything.