Please answer this correctly

Ben and cam are scuba diving. ben is 15.815.8 meters below the surface of the water. cam is 4.24.2 meters above ben. what is cam's position relative to the surface of the water? choose 1 choose 1 (choice a) a 11.611.6 meters above the surface of the water (choice b) b 11.611.6 meters below the surface of the water (choice c) c 2020 meters above the surface of the water (choice d) d 20 meters below the surface of the water

If the equation of a perpendicular bisector of a triangle is y = 2x + 7, what is the slope of the side that it is bisecting? explain how you know. 

The library sells 376 books at its annual used-book sale. the sale takes in a total of $2119. children's books cost $4, and adult books cost $7. let x = number of children's books sold, and let y = the number of adult books sold. which system of equations can the librarians use to model this situation?