Question 882873
All of this is wrong because the first step is wrong, because of sign mistake.

{{{y=5x-7}}}
{{{4x-3(5x-7)=2}}}
{{{4x-15x+21=2}}}
{{{-11x+21=2 }}}


Starting fresh from the second equation,
{{{5x+y=-7}}}
{{{5x-5x+y=-7-5x}}}
{{{0+y=-7-5x}}}
{{{highlight_green(y=-5x-7)}}}, different formula for y than before.  You will use this formula again later...
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Now, use the first equation of your system and substitute for y to find x.
{{{4x-3y=2}}}
{{{4x-3(-5x-7)=2}}}
{{{4x+15x+21=2}}}
{{{19x+21=2}}}
{{{19x=-19}}}
{{{highlight(x=1)}}}


Use what you found for x to compute the value for y.