[tex]x-\ children\\
y-\ adults\\\\ \left \{ {{x+y=2200} \atop {1,5x+4y=5050}} \right. \\\\x=2200-y\\\\Substitution:\\
1,5(2200-y)+4y=5050\\
3300-1,5y+4y=5050\ \ \ | subtract\ 3300\\\
2,5y=1750\ \ \ | divide\ by\ 2,5\\\\y=700\\\\
There\ were\ 700\ adults \ and\ 1500\ children.[/tex]