Hello!
There is not a defined number of solutions.
Why?
Since we have a single equation with two unknowns, we will have infinite solutions.
When we have more unknowns than equations we will always have infinite solutions. The only thing we can be sure is that the result will always depend on the value we assign to each variable.
A linear equation with two unknowns will always have infinite solutions and can be graphically represented by a straight line.