How do I answer this

Aball is dropped from a height of 10m above the ground. it bounce to 90% of its previous height on each bounce. what is the approximate height that the ball bounce to the fourth bounce?

Rewrite the following quadratic functions in intercept or factored form. show your work. f(x) = 3x^2 - 12

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?