Rachel is 15 years older than her sister Rebecca. She is also 4 times as old as Rebecca

Answer 1

I assume you meant to ask for the two ages.

x = Rachel's age

y = Rebecca's age

x = y + 15

x = 4y

Plug 4y into the top equation for x and get

4y = y + 15 ⇒

y = 5

x = 4y = 4(5) = 20

x = 20

Test the answer.