Question

Suppose y varies inversely with x. If y = 4 when x = 14, what is the value of y when x = 21?

Answer 1

since y=kx, y/x=k, so it is constant. You want y such that

y/21 = 4/14
y = 6

k = 2/7, but you don't need to know that to solve this kind of question.