1 When the son is 9 years old, the father's age is exactly four times that of his son. Because my father is 36 years old.

1 235 yuan

Twenty-five thousand yuan

Articles 3, 47 and 53

415km

Grandpa won six sets and grandson won two sets.

6 More than three hours and twenty minutes (24/7)

7 10 hectare

33 people got married and 84 people died.

9 lost money

10 80 km

11255m

12 20 ,24, 44, 1 1

1 a= 7