Question 77237
Simply substitute -4 in for every x

{{{7x - 5 + 3x = 6 + x - 10}}}

{{{7(-4) - 5 + 3(-4) = 6 + (-4) - 10}}}

{{{(-28) - 5 + (-12) = 2 - 10}}}

{{{(-28) + (-17) = -8}}}

{{{-45 = -8}}} 

Since this is not true, x=-4 is not a solution