Proof Writing · Medium problem

If $x$ is irrational or $y$ is rational, then $x + y$ is rational.

If $x + y$ is rational, then $x$ is irrational or $y$ is rational.

$x$ is rational and $y$ is irrational and $x + y$ is rational.

If $x + y$ is irrational, then $x$ is rational and $y$ is irrational.