how to write text in equation in latex code example

Example 1: latex normal text in equation

\usepackage{amsmath}
$...\text{normal text}...$

Example 2: normal text in equation latex

\usepackage{amsmath}
$123 \text{stuff to type} 123$

% Without amsmath package:
$123 \textrm{stuff to type} 123$