\(x-\ adult\ tickets\\\\y-\ student\ tickets\\\\
\left \{ {{x+y=1246} \atop {5x+1y=2874\ \ | *(-1)}} \right. \\\\ \left \{ {{x+y=1246} \atop {-5x-1y=-2874}} \right. \\+--------\\\\addition\ method\\\\
-4x=-1628\ \ \ | divide\ by\ -4\\\\ x=407\\\\ y=1246-x\\\\
y=1246-407=839\\\\ There\ were\ 407\ adult\ tickets\ and\ 839\ student\ tickets.\)