Examples:

`$\frac{1}{x+1}$`

`$e^{i \pi} + 1 = 0$`

`$\mathbf{E}\cdot\mathrm{d}\mathbf{S} = \frac{1}{\varepsilon_0} \iiint_\Omega \rho \,\mathrm{d}V$`

N.B. If you wish to use the dollar sign in your question, here is how you can obtain it, without messing up your LaTeX format.

` $$ 500 or \$ 500`