No solution or infinitely many

When the variables cancel, look at what remains. A false statement like $3=5$ means no number works. A true one like $3=3$ means every number works.

Move the slider. The two sides never match, because the right side is always 3 more. On a graph, these are parallel lines.

Work through it

Watch out for this

$x=x+2$ has solution $x=0$.

Check it: $0=2$ is false. Getting a 0 somewhere doesn't make it a solution.

Your turn