Answer:
The number of race entries must be at least 1800.
Explanation:
Suppose, the number of race entries is

It receives $75 per race entry. So, the total amount received from the race entries

It also receives $10000 in donations. So, the total amount received

Now, it must spend $25 per race entry to cover the cost of the race. So, the total amount spend for all race entries

Given that, the charity needs to raise at least $100,000. So, the inequality will be........

So, the number of race entries must be at least 1800.