Question 1095806
Slope of first pair:  {{{(k+5)/(-2)}}}


Slope of second pair:   {{{-6/7}}}


Lines to be perpendicular means  product of slopes {{{-1}}}.
{{{(-(k+5)/2)(-6/7)=-1}}}

{{{((k+5)/2)(6/7)=-1}}}

{{{3(k+5)/7=-1}}}

{{{3k+15=-7}}}

{{{3k=-7-15=-22}}}

{{{k=-22/3}}}

{{{highlight(k=-7&1/3)}}}

(still need to be rechecked)