If y varies with x, and y equals 10 when x equals 4, find when y equals 80

How do i work this problem out using the equation a=pe^rt

Find the height of a square pyramid that has the volume of 32 ft.³ and a base lengthof 4 feet

Aheated piece of metal cools according to the function c(x) = (.5)x ? 7, where x is measured in hours. a device is added that aids in cooling according to the function h(x) = ? x ? 2. what will be the temperature of the metal after two hours?