Answer:

Step-by-step explanation:
Let n represent number of new members and f(n) represent membership money.
We have been given that there are currently 20 members in the school's Ski Club. So when n new members join, the total number of members would be
.
Since for each new member recruited the dues for all members will be reduced by 10 cents, so new dues would be
.
The membership money would be number of total members times dues as:

Since we need our equation in standard form, so we will use FOIL to expand our equation as:




Therefore, our required equation would be
.