From the information given, the temperature given is -21, -7.8, -14.3 and -7.2
We see that none of these temperature readings are above 0 degrees Celsius, all are below therefore we can go ahead and treat them uniformly.
We will add them together without their minus sign and calculate the average, so:
21.1 + 7.8 + 14.3 + 7.2 = 50.4
We divide the answer by 4, so:
50.4 ÷ 4 = 12.6
We now revert back to our minus sign so the average 6.00 am temp is -12.6 °c
