How to calculate the equivalent weight of a metal in a metal sulphate?
I assume that if you are dealing in equivalent weights then you must be well associated with the concepts of equivalents.
Now,
$$ \textrm{equivalent} = \textrm{weight} / \textrm{eq. weight}$$
and since compounds combine in equal amounts of equivalents we have
$$\frac{\textrm{weight of metal}}{ \textrm{eq weight}} = \frac{\textrm{weight of sulphate}}{ \textrm{its eq weight}}$$
$$\rightarrow 2/x = 2.6/48$$
Hence $x= 39.92$.