Помогите решить!пожалуйсто !!

1)
$-12\ \textless \ a\ \textless \ 10\\-24\ \textless \ 2a\ \textless \ 20\\-50\ \textless \ -5a\ \textless \ 120\\-10\ \textless \ -a\ \textless \ 12\\-3\ \textless \ {a\over4}\ \textless \ 2.5\\-7\ \textless \ a+5\ \textless \ 15$

2)
$4\ \textless \ x\ \textless \ 5\\-2\ \textless \ y\ \textless \ -1\\2\ \textless \ x+y\ \textless \ 4\\5\ \textless \ x-y\ \textless \ 7\\-10\ \textless \ xy\ \textless \ -4$