# Custom numbering of Equations [duplicate]

Hi i am having a problem making a custom tag for this equation

\begin{equation*}\label{eq:3}
C_1 = \theta \left(Y_1^L -T_1+\frac{1}{1+r}(Y_2^L+T_2)+V_1\right) \tag(3)
\end{equation*}


I want to refer to an equation from a book (as part of my class) which i called equation 3. But i simply can't change it without getting a lot of syntax errors.

I have tryed different things form the forum, but so far without luck.

Hope you can help.