they receive 25 per entry but 5 goes towards the cost of the race
so 25-5 = 20 per entry is for the charity
so 20x + 5000 = 25000
subtract 5000 from each side
20x= 20000
divide both sides by 20
x = 20000/ 20
x = 1000
they need at least 1000 entries to make 25000
so to make more than 25000, they need 1001 entries