need help in solving

The Demon Drop at Cedar Point in Ohio takes riders to the top of a tower and drops them. A function that approximates this ride is h= -1612 + 641 + 60, where h is the height in feet and + is the time in seconds. About how many seconds does it take for riders to drop 60 feet? The percent of U.S. households with high speed Internet h can be estimated by h = -0.2n2 + 7.2n + 1.5, where n is the number of years since 1990. Use the Quadratic Formula to determine when 20%% of the population will have high speed Internet