Explanation:
y = 3x - 5
y = 3x + 5
a solution to this means, there is at list one value of x, for which both equations deliver the same y.
to find this we are saying both y are equal and solve for x :
3x - 5 = 3x + 5
-5 = 5
that is not true in any case and for any values of x.
therefore, there is no solution.
graphically you can imagine :
both functions are lines with the same slope or inclination. so, they are parallel. but have an offset from each other.
parallel lines will never cross (but they need a crossing point to have a common solution).
so, again, no solution.