Question

[Hải Đăng]

Mary is 12 years old. Her father is 4 times  as old as she.
Their average age is  years old

Answer 1

[Đinh Tuấn Việt]

Mary's father's age:

\(12\times4=48\) (age)

Whole their age:

\(12+48=60\) (age)
Their average age is:

\(60\div2=30\) (age)