The mean temperature of Monday to Wednesday was 37 degree Celsius and of Tuesday to Thursday was 34 degree. What was the temperature on Thursday?
I. The temperature on Thursday was $$\frac{4}{5^{th}}$$ that of Monday.
II. The mean temperature of Monday and Thursday was 40.5 degree Celsius.
III. The difference between the temperature on Monday and that on Thursday was 9 degree Celsius.

Let the temperature on Monday, Tuesday, Wednesday and Thursday be a,b,c and d respectively

It is given that a+b+c = 3*37 = 111...(I)

              and b+c+d = 3*34 = 102 ... (II)

Using statement (I) alone we get $$d\ =\ \ \frac{\ 4}{5}a$$. Which can be put in eqn (I), after which we can obtain the value of d

Using statement (II) alone we can add eqn(I) and eqn(II) to get value of b+c and it can be used to get value of d from eqn(II)

Using statement (III) alone we a-d = 9 which can be obtained by eqn(I) and (II) and n hence no new information is given. Statement (III) is no sufficient to get the required answer.