Is –3 a solution to the equation 4x – 3 + 2x = 4 + x – 8

To find out, replace x with -3:

Left side:     4x - 3 + 2x  =  4(-3) - 3 + 2(-3)  =  ?

Right side:   4 + x - 8  =  4 + (-3) - 8  =  ??

Does the answer for  ?  match the answer for  ?? 

If they match, -3 is an answer; if they don't match, then -3 isn't an answer.