What step is justified by associative property

At the newest animated movie, for every 9 children, there are 4 adults. there are a total of 39 children and adults at the movie.

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

How do i put 3(x+7) in distributive property