All the members of a construction crew work at the same pace. six of them working together are able to pour foundation in 22 hours. how many hours would this job take if the number of workers increased by factor of 2?

What is the first step of an indirect proof of a number that is divisible by two

Ineed me i stuck and i don’t want to get it wrong

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?