Answer:
Let's start by translating the sentence into an equation using algebra.
Let's say the number is represented by "x".
According to the problem:
"Twice a number" can be written as "2x".
"If twice a number is decreased by 13" can be written as "2x - 13".
"The result is 9" can be written as "= 9".
Putting it all together, we get the equation:
2x - 13 = 9
Now we can solve for x:
2x = 22
x = 11
Therefore, the number is 11.