Substitute either equation into the other to solve. I'm going to substitute the second equation for the value of y in the first:
2x + (1/3x +1) = -6
(7/3x) + 1 = -6
7/3x = -7
x=-3
y=0
The graph plots 2x + y = -6 as blue and y =1/3x +1 as orange
Math