To get the y coordinate that goes with the x-coordinate of 50, substitute 50 into the equation for x:
y = 3(50)-4
Now, solve for y by multiplying 3 times 50 and then subtracting 4:
y = 150 - 4
y = 146
So, now you know the y coordinate is 146 when the x coordinate is 50.
Hope that helps!