y=3x + 2
This form represents an affine function, graphically represented by a straight line (y = mx + b)
All you need to do is replace "x" by -2 in 3x + 2, and you'll find the value of y.
y = 3x + 2
y = 3 * (-2) + 2
y = -6 + 2
y = -4
So when x = -2, y = -4. Graphically, x and y represents the coordinates of a point belonging to the line of y=3x+2 (I represented the graphic and the bottom of the answer)
Hope this Helps! :)