SOLUTION: Mary is n years old. In 10 yrs how old will Mary be? How old was she 7 years ago?

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Question 746929: Mary is n years old. In 10 yrs how old will Mary be? How old was she 7 years ago?
Answer by Chipmonkcheeks(3) About Me  (Show Source):
You can put this solution on YOUR website!
Lets say Mary is 20 years old. Then 7 years ago she would have been 13 years old
that is
+20+-+7+=+13+
In 10 years time Mary will be 30, that is:
20+%2B+10+=+30+
So lets do the same thing but instead of saying Mary is 20 years old, we will say Mary is n years old.
Then 7 years ago Mary would have been n+-+7 years old.
In 10 years time Mary will be n+%2B+10 years old!
Simplez