Let x represent the number.
A number is taken away from 13:
13 - x
The result is 4:
13 - x = 4
to find the number, Let's solve for x:
13 - x = 4
Subtract 13 from both sides:
13 - 13 - x = 4 - 13
-x = -9
Divide both sides by -1:

Therefore the number is 9
If 9 is taken away from 13 the result is 4
ANSWER:
9