Answer
(a) $T(4) = 16, T(15) = 24$
(b) $H(t) = T(t-1)$ will cause any change in temperature to occur one hour later since subtracting $t$ by 1 will shift the graph to the right by 1 hour.
(c) $H(t) = T(t)-1$ will lower the temperature by one degree at any given hour since subtracting $T(t)$ by 1 will shift the graph down by 1 degree.
Work Step by Step
(a) $T(4)$ and $T(15)$ can be found by looking at the graph
(b) Subtracting from $t$ causes a left to right translation, which in this graph will shift the time but not the overall temperature.
(c) Subtracting from $T(t)$ causes a up to down translation, which in this graph will lower the temperature for all hours.
