Sulfur has 6 electrons, so we put 6 in the first spot.
Oxygen has 6 electrons too, but since there are 3, we would multiply 6 times 3 , which equals 18, then add that too.
The 2 is added because there is that negative 2 at the top of the formular, which indicates the presence of two extra valence electrons.
the equation would be
6 + 18 + 2 = 26