Question

A worker record the temperature T°C at various time on a certain winter day. He found that the temperature was 5°C, 8°C and 7°C at 2 hours, 4 hours and 6 hours after 9 am respectively. Find an expression for T at time T hours after 9 am.

Answer 1

Find an expression

Answer 2

You cannot use T for both time and temperature!
since the variation is not linear, you will need to approximate.
It dropped one degree in the last 2 hours, so at that same rate,
temp = 7 - 1/3 T

Actually, I suspect a typo.