Suppose $a$ is directly proportional to $b$, but inversely proportional to $c$. If $c$ when $b = 5$ and $c =9$, then what is $c$ when $b=3$?
a = k b/c sub in values given to calc k the proportionality constant
then use it in the subsequent proprtions..... but it appears your question is missing some info or typed incorrectly....