Plz guys answer this question, it won’t take long to answer this question so plz plz answer my question, plz show all the working and THANK YOU SO MUCH Answer a and b

I posted this question 1000 times plz answer guys

How do you solve a question like this?

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?

Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?