Hello from MrBillDoesMath!
Answer:
The number = 15
Discussion:
Let the number be "n". The question states that
n - 9 = 6
as "decreased by 9" means 9 less than the number or subtract 9 from the number. Now add 9 to both sides:
n - 9 + 9 = 6 + 9 =>
n = 6 + 9 = 15
where we used (-9 +9) = 0
Thank you,
MrB
