Anumber decreased by 9 is equals to 6?

Hello from MrBillDoesMath!

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

d. 9

step-by-step explanation:

54/12 = 4.5

sf = 4.5

so x = 2 · 4.5 = 9

i believe the answer is the polygon, heptagon.