Tony is 21 years older than his sister Danielle. In 13 years he will be twice as old as Danielle. How old is each of them now?

Question

Mathematics

Quentin Aguilar

5 July, 04:47

Tony is 21 years older than his sister Danielle. In 13 years he will be twice as old as Danielle. How old is each of them now?

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Answers (1)

Know the Answer?

Landon Walter · Answer 1

x-y=21 ⇒ x=y+21

x+13=2y

Substitute y+21 for x into the equation x+13=2y

So y+21+13=2y

Simplify 34=y

So Danielle is 34 years old. Plug y back in to the original equation

x-34=21

x=55

Tony is 55 years old