Matthew is 7 years older than twice the age of his sister. if matthew is 13, how old is his sister?

3

4

10

33

Let sister be s.  Matthew, M

Matthew is 7years older than twice the age of his sister

M = 7 + 2s

13 = 7 + 2s.   7 crosses the equality to other side and becomes -7

13 - 7 = 2s

6 = 2s    Divide both sides by 2

6/2 = 2s/2

3 = s

Sister is 3 years old.

I’m pretty sure the answer is a