Substitute any number to 'A'. Then divide it to the number of the members of the Middle school math club, which is 11, to be able to know if your answer is correct.
For example, substitute '2' to 'A'. The amout they paid their speaker will now be '$122'. Divide it to 11. And the answer is '$11' which is the same amount each member paid the guest speaker.
HOPE IT HELPS!