Xiao Ming is 8 years old. He is 81 years old with his parents______ Three years later, their average age was 34, when Xiao Ming______ I'm 40 years old

Xiao Ming is 8 years old. He is 81 years old with his parents______ Three years later, their average age was 34, when Xiao Ming______ I'm 40 years old

(34 × 3-81) / - 3, = (102-81) / - 3, = 21 / - 3, = 7 (years), 8 + 7 = 15 (years). A: seven years later, their average age is 34, and Xiaoming is 15. So the answer is: 7; 15

Father and mother are 72 years old this year. How many years later, their average age is 42 years old?

(42 × 2 - 72) △ 2 = 12 △ 2 = 6 (years); a: after 6 years, their average age is 42

Father and mother are 72 years old this year. How many years later, their average age is 42 years old?

(42 × 2 - 72) △ 2 = 12 △ 2 = 6 (years); a: after 6 years, their average age is 42