It isn't at all!
When dividing numbers, the easiest way is to imagine the values as a fraction, and then reduce that fraction. If it reduces to a core fraction (ones that you should know their decimal value without thinking), then you have your answer.
[tex] \frac{12}{15} = \frac{4}{5} = 0.8 [/tex]
We simplified our fraction by dividing the numerator and denominator by 4, which left us with [tex] \frac{4}{5} [/tex], which we know is equal to 0.8.
You may be confused thinking that 0.8 is the same as 8. 0.8 is actually a tenth of the value of 8. This makes them very different values.
Below, I have also included a picture to help you memorize your common/core fractions. I recommend learning these as they will help you get through all sorts of math, from Geometry to Calculus!
