1) y = kx . . . . . for some constant k
.. Here y is directly proportional to x , where k is the constant of proportionality
2) y = k/x . . . . for some constant k
.. Here y is inversely proportional to x , again k is the constant of proportionality.
3) y = 2x +52
..
Here y is linearly related to the x , it is neither directly proportional nor inversely proportional.