Let X represent Nick's age and Y represent Sara's age.
Then, it is given that: Nick is four years older than Sara.
We write the statement as:
or
The only ordered pairs (X,Y) which satisfy the equation are: (0,-4) and (4,0) as you can see in the graph also.
In the graph X axis represents the age of Nick's age and Y-axis represent the age of Sara's age and the line Y=X-4 represents the relationship between the age of both.
Let and be independent random variables representing the lifetime (in 100 hours) of Type A and Type B light bulbs, respectively. Both variables have exponential distributions, and the mean of X is 2 and the mean of Y is 3.