Question

Sam is 5 years old. His older brother, Tom, is three times as old as Sam. When Sam is 20, how old will Tom be?

Answer 1

To find the age of tom we will use the expression 20*3 because tom is three times as old as Sam. 

so the answer is 60

Answer 2

Sam is 5
Tom is 5 x 3 = 15

15 years later Sam is 20 (5 + 15 = 20)
Add 15 to Tom's age (15 + 15 = 30)
Tom is 30