there are 90 chairs arranged for people to watch a band concert. if 75 chairs have people in them during the concert, what percentage of the chairs are fiilled​

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?