The idea is to divide distance by time.

The idea is to divide the distance by the time.

To calculate the reciprocal of any expression, divide 1 by that expression.

Its actually a French expression - idee fixe which means a fixed idea, an obsession.

If you divide a rational expression by another rational expression, you will again get a rational expression.

The answer will depend on what you wish to divide it by. If you wish to divide it by a variable, y, then the relevant expression is x/y.