You have to remove your quotes or use backticks such:
CREATE DATABASE mynewdb;
or
CREATE DATABASE `mynewdb`;
Backticks are to be used for database, table and column identifiers, but are only necessary when the identifier is a MySQL reserved keyword, or when the identifier contains whitespace characters or characters beyond a limited set (see below) It is often recommended to avoid using reserved keywords as column or table identifiers when possible, avoiding the quoting issue.
Here a very good answer When to use single quotes, double quotes, and backticks in MySQL.