Question 923974
{{{x - y = 5}}}......eq.1 

{{{x + 11y = -16}}}....eq.2
____________________________________subtract eq.2 from eq.1

{{{x - y-(x + 11y) = 5-(-16)}}}

{{{cross(x) - y-cross(x) - 11y = 5+16}}}

{{{ - 12y = 21}}}

{{{ y = 21/-12}}}

{{{ y = -21/12}}}

{{{ y = -1.75}}}

go to {{{x - y = 5}}}......eq.1 plug in {{{ y = -1.75}}}

{{{x - (-1.75) = 5}}}

{{{x +1.75 = 5}}}

{{{x  = 5-1.75}}}

{{{x  = 3.25}}}

solution: ({{{3.25}}},{{{-1.75}}})


see it on a graph:


{{{drawing( 600, 600, -10, 10, -10, 10,circle(3.25,-1.75,.12),locate(3.25,-1.75,p(3.25,-1.75)), graph( 600, 600, -10, 10, -10, 10, x-5, -x/11-16/11)) }}}