-x on both sides to get
x=15
We are given these three people age below:
- Jim's age
- Carla's age
- Tomy's age
We define the age of Jim as any variable, because the problem doesn't give any specific age. I will define Jim's age as x.
Next, Carla is 5 years older than Jim. That means if Carla is 5 years older, her age would be x+5.
Then Tomy is 6 years older than Carla. That means the age would be 6+(x+5).
The sum of their three ages is 31 years old. That means we add all these ages and equal to 31.

Combine like terms and solve for x.

Then we substitute the value of x in ages to find these three people ages.
- Jim's age = x = 5
- Carla's age = x+5 = 5+5 = 10
- Tomy's age = 6+(x+5) = 6+(5+5) = 6+10 = 16.
Answer
- Jim's age = 5
- Carla's age = 10
- Tomy's age = 16
Degree days are the difference between the daily temperature mean, (high temperature plus low temperature divided by two) and 65°F. 65°F because we assume that at this temperature we do not need cooling or heating.
In our case the daily mean temperature is 83°F and X is the number of cooling-degree days.
X=83-65
X=18