Question 117989
The easiest way to solve this would be to isolate the y variable in the equation 3x+y=4
-3x+3x+y=4-3x
y=-3x+4
Now substitute -3x+4 in the other equation in place of y
4x+2(-3x+4)=4  Distribute
4x+-6x+8=4  add like terms
-2x-8=4  add -8 to both sides
8+-2x-8=4-8 
-2x=-4  multiply both sides by -1/2
x=2
Go back and subtitute 2 for x in the other equation
3(2)+y=4
6+y=4
y=-2
Now to check your answers, go back and subtitute these values for x and y in either equation and see if they come out equal to 4.
3(2)+(-2)=4
6+-2=4
4=4
your answer is {2,-2} 
make sure you put those values in a solution set and not as an ordered pair