documentclass{article}
usepackage{amsmath}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{setspace}
usepackage{color}
usepackage[hmarginratio=2:2]{geometry}
usepackage{epstopdf}
usepackage{afterpage}
usepackage{ upgreek }
usepackage{mathtools}
begin{document}
begin{equation}
frac{lim_{Updelta tto0} Pbigg[splitfrac{
text{an individual fails in the interval} (t, t+Updelta t),}{text{given the individual has survived to t} }bigg]}
{Updelta t}
end{equation}
end{document}