Heres what i did for this one. find an equation relating work + math = 16 (total hours she has in a day). so math = 16 - work (i plug that into the equation for h) and for money, i have y = 6*work + 6 i plug this in as well and take the derivative. i get f ' = -4/3 *(6worrk + 6)^-2/3 (16-work)^-1/3 critical points work = -1, 16. the answer is it hits a max at 14/3 hours. what am i doing wrong? i really just need some hints, i have no idea how to get started. thanks!