How many times in a 12 hour period does the sum of the digits on a digital clock equal 6?

Fred and gene are hang gliding. fred is 700 feet above the ground and descending at 15 ft/s. gene is decending as shown in the table. interpret the rates of change and initial values of the linear functions in terms of the situations they model. show all work. freds equation is f(x)=-15x+700. ( genes is the table attached)