Answer:
45 people are members at the tennis club
Explanation:
Let the number of people in the tennis club be denoted as "x".
Since each of them donated $12.45, then total donated = 12.45x
Since they had $50.25 left over after paying the cost of $510 for the ball, then;
12.45x - 510 = 50.25
12.45x = 510 + 50.25
12.45x = 560.25
x = 560.25/12.45
x = 45