$$ y'+3y+4z=2x $$ $$ z'-y-z=x $$ x is independent variable!
The solution I get is not the same as the one on Wolfram Alpha http://www.wolframalpha.com/input/?i=y%27%2B3y%2B4z%3D2x%2C+z%27-y-z%3Dx . So how to solve it? My solutions are: $$ y=C1e^{-x}+C2xe^{-x}-6x+10 $$
$$ z=-(C1/2)e^{-x}-(C2/4)e^{-x}-(C2/2)xe^{-x}+2x $$