documentclass[a4paper,12pt]{article}
usepackage{amsmath,amssymb}
begin{document}
[U=left{(u,v),Biggvert, begin{matrix} u, vcolon mathbb{R}^dto[0,infty) \
text{bla bla bla}\
u+v<7
end{matrix}right}
]
end{document}