SOLUTION: Zoron is ten years older than his sister. In three years, he will be twice as old as she will be then. How old are they now?

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Question 510514: Zoron is ten years older than his sister. In three years, he will be twice as old as she will be then. How old are they now?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let z = Zoron's age now
Let s = his sister's age now
given:
+z+=+s+%2B+10+
+z+%2B+3++=+2%2A%28+s+%2B+3+%29+
-------------------
By substitution:
+s+%2B+10+%2B+3++=+2%2A%28+s+%2B+3+%29+
+s+%2B+13+=+2s+%2B+6+
+s+=+13+-+6+
+s+=+7+
and
+z+=+s+%2B+10+
+z+=+17+
Zoron is 17 and his sister is 7
check:
In 3 years, he will be 20 and she will be 10
OK