Answer: Paul will be 30 years old
Step-by-step explanation:Let the age of her sister be x, then from the given data
=> 4x = 20
=> x = 5 years
The age of her sister is 5 years
In the second case, paul is twice as old as his sister
=> Age of paul = 2(x)
=> Age of paul = 10 years
Paul will be 10 years old when he is twice as old as his sister