The outdoor temperature was 8 degrees at midnight.The temperature declined 5 degrees during each of the next 3 hours. What was the temperature at 3...

The outdoor temperature was 8 degrees at midnight (12:00 a.m.).

The temperature declined (or decreased) 5 degrees during each of the next 3 hours.

What was the temperature at 3:00 a.m. ?

At 12:00 a.m. the temperature was 8 degrees. During the first hour the temperature decreased by 5 degrees. This means at 1:00 a.m. the temperature was 8 degrees - 5 degrees = 3 degrees.

During the second hour the temperature decreased by another 5 degrees.  This means at 2:00 a.m. the temperature was 3 degrees - 5 degrees =-2 degrees. 

During the third hour the temperature again degreased by another 5 degrees. This means at 3:00 a.m. the temperature was -2 degrees -5 degrees =-7 degrees. 

The temperature at 3:00 a.m. was -7 degrees.