Ans: A
$\left\{ \begin{array}{ll}
2p+q=3 & \ldots \unicode{x2460} \\
p-q = 3 & \ldots \unicode{x2461}
\end{array} \right.$
$\left\{ \begin{array}{ll}
2p+q=3 & \ldots \unicode{x2460} \\
p-q = 3 & \ldots \unicode{x2461}
\end{array} \right.$
$\unicode{x2460}+\unicode{x2461}$, we have
$\begin{array}{rcl}
3p & = & 6 \\
p & = & 2
\end{array}$
Sub. $p=2$ into $\unicode{x2460}$, we have
$\begin{array}{rcl}
2(2) + q & = & 3 \\
q & = & -1
\end{array}$
