Example 4Being at least 30 years old is necessary for serving in the U.S. Senate. If you are under 30 years old, then it is impossible for you to be a senator. That is, if you are a senator, it follows that you must be at least 30 years old.
Example 4Being at least 30 years old is necessary for serving in the U.S. Senate. If you are under 30 years old, then ,it is impossible for you to be a sena?tor. That is, if you are a senator, it follows that you must be at least 30 years old.