Question

Which system of equations below has exactly one solution?

Answer 1

Third.
since all other have infinite solutions,
because they are written in a different way. slight arrangements can form other equation.
though, the first system has no solution. as they have same slope (parallel) but different intercepts.

Answer 2

That is the third choice.

If we add the 2 equations we get

2y = -12 so y = -6

substituting in one of the equations we get x = 0