and the reason why it's 16 is that 16 golf balls are equal to 24 dollars and he can't purchase 17 golf balls or else that would be $25.50 which is more money than he has.
Lucy studies one less (-1) than twice the number of hours a week that rose studies (2 * R), lucy studies 11 hours a week. What we do is add 1 hour to lucy's 11, to get 12, then divide by 2 as lucy studies twice the hours. 12 / 2 = 6.