# I want put the text on the left and the equation on the middle

\begin{align}
\Delta U=Q+W\nonumber\\
\text{Le transformation est adiabatique alors} :\nonumber\\
W_{compresseur}\:=m\:C_{v}\:\Delta T
\end{align}


I want put the text in the left and all the equation are aligned by the '=' symbol, please

• Welcome to TeX.SX! You don't use any &, so there's no alignment. Could you please make your example compilable (make it a MWE)? – TeXnician Jul 21 '18 at 12:31
• Unrelated, but you should code W_{\text{compress}} for a correct letterspacing of the word ‘compresseur’. – Bernard Jul 21 '18 at 12:38

You are looking for \intertext:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{align}
\Delta U&=Q+W\nonumber
\intertext{Le transformation est adiabatique alors :}
W_{compresseur}&=m\:C_{v}\:\Delta T
\end{align}
\end{document}


Note, it's not necessary to use \\ or \nonumber after intertext. You don't need \\ before it as well.