"a rise of a quarter from last year" means the percentage went up by 25%
x = old value
x + 25% of x = x + 0.25x = 1.25x = new value = 0.25 since "1 in 4" means 1/4 = 0.25
So,
1.25x = 0.25
x = 0.25/1.25
x = 0.2
x = 2/10
x = 1/5
Answer: The fraction of families that owed money is 1/5, or 1 in 5.