The ratio of students to teachers at a school is 19 : 1. At this school, there are 400 people (teachers and students). How many of these 400 people are students? (enter number only, without the unit)

Ineed with number 17 i don’t get it at alll

The boiling point of water at an elevation of 0 feet is 212 degrees fahrenheit (°f). for every 1,000 feet of increase in elevation, the boiling point of water decreases by about 2°f. which of the following represents this relationship if b is the boiling point of water at an elevation of e thousand feet? a) e = 2b - 212 b) b = 2e - 212 c) e = -2b + 212 d) b = -2e + 212

What number is 7 units left of -15?