Answer :
[tex]25+30h=5h^2-10\\
5h^2-30h-35=0\\
5(h^2-6h-7)=0\\
h^2-6h-7=0\\
h^2+h-7h-7=0\\
h(h+1)-7(h+1)=0\\
(h-7)(h+1)=0\\
h=7 \vee h=-1\\\\
\boxed{h=7}[/tex]
After 7 hours.
After 7 hours.