Yes- that you should show some effort yourself first! All you are asked to do is subtract two functions. One thing to be carfule about- the variable "t" in the two equations represent two different things. In the formula for "T", t is "hours after 6.00 am" while in the formula for " ", t is "hours after midnight".
If we call the "t" in the formula for T t' so we can distinguish then t'= t- 6 because, of course, 6 am is 6 hours after midnight.