1. ## Find the average

The average age of the people in a certain group was 16 years before one of the members left the group and was replaced by someone who is 12 years older than the person who left. If the average age of the group is now 18 years, how many people are in the group?

I know it's 6 but how do you show it?

2. ## Re: Find the average

Originally Posted by donnagirl
The average age of the people in a certain group was 16 years before one of the members left the group and was replaced by someone who is 12 years older than the person who left. If the average age of the group is now 18 years, how many people are in the group? I know it's 6 but how do you show it?
Solve this system $\frac{\Sigma }{n} = 16\;\& \;\frac{{\Sigma + 12}}{n} = 18$ for $n~.$