How can you tell if a system of equations has infinite solutions?

To tell if an equation has infinite solutions, the equation will be equal to each other.

For example,

x = x

x + 1 = x + 1

x - y = x - y

And so on ...

And in special cases,

0x = 0

0x = 0 (y + 1)

They have infinite solutions because there's no constant to determine the variable.