How do you find the sum of interior angles?

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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?

Find the constant of variation for the relation and use it to write an equation for the statement. then solve the equation.