Final answer:
To find the average temperature for the day, add the high and low temperatures and divide by 2.
Step-by-step explanation:
To find the average temperature for the day, you need to calculate the mean temperature. The mean temperature is found by adding the high and low temperatures and dividing by 2.
For this question, the high temperature is 90 degrees and the low temperature is -20 degrees.
So, the average temperature for the day would be (90 + (-20)) / 2 = 35 degrees.