I am ten years older than my sister. There was a time when I was three times older than she was, and in one year I will be twice as old as she is. What is my age now?
Answer
I am 19 years old and my sister is 9.
Let x = my sister’s age and y = my age.
y = x + 10
y + 1 = 2(x + 1)
y = 2x + 1
Substituting this result in our first equation, we have:
2x + 1 = x + 10
x = 9
so y = 19
When my sister was 5, I was 3 times older than she was.