To solve this problem you must apply the proccedure shown below:
1. You have the following points given in the problem above:
2. To find the midpoint, you must apply the formula that is used for calculate it. This is:
Where:
3. Now, you must substitute these values into the formula for calculate the midpoint, as following:
Therefore, the answer is: 
Answer:
6 ft 1 inch
Step-by-step explanation:
We know that there are 12 inches in a foot. So we divide 73/12, which gives us 6 remainder 1. So there are 6 ft and 1 inch.
Let s be the son's age 15 yeasr ago and m the mother's age that year.
We also know that:
Plotting vallues:
Remember that they were that age 15 years ago.
So their actual age is 30 and 60.
(original - new)/original * 100%
(48-15)/48 * 100%
33/48 *100%
68.75 % decrease
