Alternative Equation Formats

$${\displaystyle \begin{array}{rclrcll}{p}_{1\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_1+p_2+p_3& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>1}& =& p_1+p_4+p_7\\ p_{2\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_4+p_5+p_6& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>2}& =& p_2+p_5+p_8\\ p_{3\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_7+p_8+p_9& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>3}& =& p_3+p_6+p_9\end{array}}$$

$${\displaystyle \begin{array}{rclrcll}{p}_{1\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_1+p_2+p_3& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>1}& =& p_1+p_4+p_7\\ p_{2\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_4+p_5+p_6& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>2}& =& p_2+p_5+p_8\\ p_{3\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>}& =& p_7+p_8+p_9& & p_{\cdot <!--\; \cdot \; --><span\; class="Comment\_comment\_\_N0+Yl"></span>3}& =& p_3+p_6+p_9\end{array}}$$

\[ \begin{array}{rclp{0.50in}rcl} p_{1 \cdot } & = & p_1 + p_2 + p_3 & & p_{\cdot 1} & = & p_1 + p_4 + p_7 \\[0.05in] p_{2 \cdot } & = & p_4 + p_5 + p_6 & & p_{\cdot 2} & = & p_2 + p_5 + p_8 \\[0.05in] p_{3 \cdot } & = & p_7 + p_8 + p_9 & & p_{\cdot 3} & = & p_3 + p_6 + p_9 \\ \end{array} \]