Answer:
Percent Decrease = 20% Decrease
Explanation:
To find percentage decrease, we will use a simple formula shown below:
Percentage Decrease/Increase =

Where
New is the latest number of members (which is 24)
Old is the initial number of members (which is 30)
Note: the multiplication by a factor of "100" brings the answer to a percentage.
Now, lets substitute the numbers and figure out the percentage decrease:

So, it comes to -20, which is a decrease of 20%