ANSWER
18.4 inches
Step-by-step explanation
There were 4 people standing shoulder to shoulder (no space in between their shoulders).
The entire length of the distance across their shoulders is 73.5 inches.
To find the average length of each person's shoulders, we need to divide the entire length (73.5 inches) by the number of shoulders there (4), that is:
That is the average length of each person's shoulder.