You should know that you can express a linear function in the form , with as the gradient and as the intercept.
Rearranging the equations gives:
If then the gradients will be the same and the lines will be parallel. Therefore there will not be a solution.
For we have
Substituting back into one or both of the equations, you will see there is only one solution.
B. If , like I said, the lines are parallel.
However if as well, the equations are in fact, identically equal. In other words, they are the same line.
C. Done in A and B - not sure if it's what you wanted...