I’m still a beginner to LaTeX, and I don’t know how to write this equation.
[Tex/LaTex] How to write this equation in LaTeX
equationsmath-mode
Related Solutions
You would probably want to use an align environment
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\label{cons1}
x_i+w_{mi}&\le X_j &&\text{if $i$ is to the left of $j$}\\
\label{cons2}
x_i-w_{mj}&\ge X_j &&\text{if $i$ is to the right of $j$}\\
\label{cons3}
y_i+h_{mi}&\le y_j &&\text{if $i$ is below of $j$}\\
\label{cons4}
y_i-h_{mj}&\ge y_j &&\text{if $i$ is above of $j$}
\end{align}
\end{document}
You shouldn't use eqnarray in LaTeX, see eqnarray vs align
In addition to the excellent suggestions above in comments section -- if you wish to do manual numbering add the \tag syntax at the end of the equation --\tag{..3.1.1a,b} \label{myeq} --the \label syntax for referencing can be plugged in if desired
Off course you can revert to auto numbering with the equation environment
And the negative points are not mine(-1)
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
{T^k}{t} =
-\frac{\dot{f}_t^k}{A\varepsilon_{\textrm{cat}}C_t^k}
\frac{T_i^k-T_i^{k-1}}{\Delta z}
+\frac{\pi D_i}{A\varepsilon_{\textrm{cat}}C_t^kC_p^k}
+\frac{\rho_{\textrm{cat}}a}{\varepsilon_{\textrm{cat}}C_t^kC_p^k}
\sum_{i=1}^{N} \eta_i^kr_i^k(-\Delta H_{\!f,i}^k) \tag{..3.1.1a,b} \label{myeq}
\]
For example, see \eqref{myeq}.
\end{document}
Best Answer
Welcome to the site. We will appreciate the questions that have a minimal working example (code) that shows the efforts you have already put. Asking somebody to do things is frowned upon here. If you have no idea of how to start, you may put the following as a MWE
and ask for the equation code. Since this is your first question, here is the code for the equation you requested and this should get you started.