The mean temperature for the first 4 days in January was 8°C. The mean temperature for the first 5 days in January was 7°C. What was the temperature on the 5th day?

Answer : The 5th day = 3 Celsius

Explanation:
the average of the first 4 day is 8
Which mean the combine temp on the first 4 day is 8 x 4 = 32

Now on the first 5 day the average temp is 7

Then the combine temp on the first 5 day is 7 x 5 = 35

Find the 5th day

4 days combine temp + 5th day = the combine temp of 5 days

32 + 5th day = 35
5th day = 35-32
5th day temp = 3C