Answer :
x - young
y - adult
[tex]12.50x+17.50y=1535\\ x+y=110\\\\ 12.50x+17.50y=1535\\ x=110-y\\\\ 12.50(110-y)+17.50y=1535\\ 1375-12.50y+17.50y=1535\\ 5y=160\\ y=32\\\\ x=110-32\\ x=78 [/tex]
y - adult
[tex]12.50x+17.50y=1535\\ x+y=110\\\\ 12.50x+17.50y=1535\\ x=110-y\\\\ 12.50(110-y)+17.50y=1535\\ 1375-12.50y+17.50y=1535\\ 5y=160\\ y=32\\\\ x=110-32\\ x=78 [/tex]