The slash must be represented as shown above, even when it is not related to division. The fraction bar separates the numerator of a fraction from its denominator. There are no exceptions. Even the simplest fraction such as one-half must be represented with fraction indicators and a fraction bar between the 1 and the 2. If you need to deal with complex fractions, give me a holler.
Indexing refers to superscripts and subscripts.
Once a level is established by one of these indicators, that level remains in effect until another level is established by another level indicator. If a symbol is indexed both by a subscript and a superscript, the subscript must be written first. A space after a symbol returns you to the base level. For first-level subscripts and superscripts, there are no further rules. The most commonly used radicaal is the square root.