Any equation in the form

\begin{equation*} a_1 x_1 + a_2 x_2 + \cdots + a_n x_n = c, \end{equation*}

where	\(a_i\)	is the \(i\)-th coefficient,
	\(x_i\)	is the \(i\)-th variable or unknown, and
	\(c\)	is some constant.

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• One variable