By default, equation numbers are place on the right side of an equation for any numbered math environment, such as equation, eqnarray, and align. Surprisingly, the equation number position can is changed through the optional documentclass argument leqno:
Left numbering
\documentclass[leqno]{article}
Right numbering (by default and therefore usually skipped):
\documentclass[reqno]{article}
Here is a minimal working example:
\documentclass[a4paper,12pt, leqno]{article}
\usepackage{amsmath}
\begin{document}
\subsubsection*{Equation:}
\begin{equation}
f(x)=ax^2+bx+c
\end{equation}
\subsubsection*{Align:}
\begin{align}
f_1(x)&=a_1x^2+b_1x+c_1\\
f_2(x)&=a_2x^2+b_2x+c_2
\end{align}
\end{document}
Align is part of the amsmath package which was used here because there are several reasons to avoid eqnarray.
and 
), however, can only be produced using the inline math mode.
.
) or complex numbers (
) are not provided by default by Latex. It doesn’t mean that Latex doesn’t know those sets, or more importantly their symbols…
for prime numbers using 
for integers using 
for irrational numbers using 
for rational numbers using 
for real numbers using 
by typing 
