[tex] \left \{ {{4p+5q=-18\ |\cdot2} \atop {3p-10q=69}} \right. \\\\ \left \{ {{8p+10q=-36} \atop {3p-10q=69}} \right. \\+-----\\\\11p=33\ \ \ \ |:11\\p=3\\\\4\cdot3+5q=-18\\12+5q=-18\\5q=-18-12\\5q=-30\ \ \ \ \ \ |:5\\q=-6\\\\ \left \{ {{p=3} \atop {q=-6}} \right. [/tex]
