How do I do this problem

Astuntman jumping off a 20-m-high building is modeled by the equation h=20-5t^2, where t is the same in seconds. a high-speed camera is ready to film him between 15m and 10m above the ground. for which interval of time should the camera film him?

Three times the sum of a number and seven is negative thirty-six. what is the number?

Find the quotient with the restriction.