Omni, please learn how to use forum editor to format correctly your equations. Attaching them as pictures doesn't make sense.
When you start a message you have a set of buttons over the edit field. Two of them are X2 and X2. If you mark part of the text and click one of these buttons, special tags are added around marked characters, and they become subscripts or superscripts.
These tags can be also added manually, and
[noparse]SO42-[/noparse]
will be displayed as
SO42-
(note: there are always two tags, opening and a closing one, opening has [tag] form, while closing has a [/tag] form; [noparse][/noparse] is for subscripts, [noparse][/noparse] is for superscripts)