Question

Another neighbor said, “My age is the difference between twice my age in 5 years and and twice my age 5 years ago.” How old is this neighbor? A third neighbor had the same claim for 17 years from now and 17 years ago. How old is this neighbor?

Answer 1

The neighbor is 20 years old.

The third neighbor is 68 years old.

Explanation:

Equations

Let's set:

x=current age of the neighbor

x+5=his age in 5 years

x-5=his age 5 years ago

He claims that his age is the difference between twice his age in 5 years and twice his age 5 years ago. Then:

x = 2( x + 5 ) - 2( x - 5 )

Operating:

x = 2x + 10 - 2x +10

Simplifying:

x = 20

The neighbor is 20 years old.

Repeating for the other neighbor, a similar equation is established:

x = 2( x + 17 ) - 2( x - 17 )

Operating:

x = 2x + 34 - 2x +34

Simplifying:

x = 68

The third neighbor is 68 years old.