Let z be any number (like x would be)
if we set z equal to 2x-6y, then we get z = 2x-6y
The system
2x-6y = 8
2x-6 = 3
turns into this new system
z = 8
z = 3
but z is a single number. It can't be both 8 and 3 at the same time. So there are no solutions
To find slope intercept form first do rise over run
rise 4 run 3
then find where it crosses the x-intercept to get
y=4/3x-3