The sum of 5 and 2x is at most 27

The sum of 5 and 2x is at most 27

The sum of 5 and 2x means we add 2x to 5:
5 + 2x

The phrase at most means less than or equal to, so we have an inequality where 5 + 2x is less than or equal to 27
5 + 2x <= 27