If a : (b + c) = 7 : 9, c : (a + b) = 9 : 11, and a + b + c = 4080, then what is the value of b?

If all the girls in school B and school C participated in the function, find the ratio between the number of boys in school B and school C who participated in the function.

Which of the following examples represents an inverse proportional relationship (reverse movement)?