There are 7 books on the floor. the number of books on the shelf is 2 more than 3 times the number of books on the floor. how many books are on the shelf?

Consider u = {x|x is a negative real number}which is an empty set? o {x|x eu and x has a negative cube root}o {x|x eu and x has a negative square root}{x|x eu and x is equal to the product of a positive number and -1}{x|x eu and x is equal to the sum of one negative and one positive number?