You can use the following basic operators in your fields' display text or in the values of your skip or validation logic.
| Operator | Description |
|---|---|
| + | Adds two values or expressions together. |
| - | Subtracts one value or expression from another. |
| * | Multiplies two values or expressions together. |
| / | Divides one value or expression by another. |
| mod | Finds the remainder after division of one expression by another. |
| | | Performs a union on two expressions. |
| and | Performs a boolean AND on two expressions. |
| or | Performs a boolean OR on two expressions. |
| = | Performs an 'equals to' comparison on two expressions. |
| != | Performs a 'not equals to' comparison on two expressions. |
| <= | Performs a 'less than or equals to' comparison on two expressions. |
| < | Performs a 'less than' comparison on two expressions. |
| >= | Performs a 'greater than or equals to' comparison on two expressions. |
| > | Performs 'greater than' comparison on two expressions. |
Also see here for more functions and expressions you can use.