how can you determine if an expression simplifies to a positive or negative value?in your response you may use but are not limited to patterns examples or descriptions of your thinking? pl help​

Valentina is subtracting from . she finds the lcd to be 15y2. what is valentina's next step?

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?

Peter measures the angles in a triangle. he finds that the angles are 95, 10 and 75. is he correct? explain your answer