When two variables are directly proportional, it means that one is a constant multiple of the other. For example, in the equation #y = 16x#, #y# is directly proportional to #x#, because #y# is just some constant multiple of #x#. (In this case, the constant multiple is 16.)
The equation #y = x^2# does not represent a directly proportional relationship, because #y# is not some constant multiple of #x#.
To the problem at hand -- we are given that #y# and #x# are directly proportional. This means #y# is a constant multiple of #x#. This can be written as #y = kx#, where #k# is some constant multiple (a number).
We have the equation #y = kx# and we are also told that #x = 2# and #y = 6#. We can directly plug these in to determine the value of #k#. #y = kx -> 6 = 2k -> k = 3#. Thus, our relationship is given by the equation #y = 3x#. This is our final answer.