Let's write 0.8 as a fraction. So 0.8, the 8 right over
here is in the tenths place. It is the tenths place. So you could read
this as 8 tenths. And we can write that literally
as being equal to 8 tenths, or 8 over 10. And now we've already written it
as a fraction, and if we want, we can simplify this down. Both 8 and 10 share
common factors. They are both divisible by 2. So lets divide both the
numerator and the denominator by 2. We are not changing the
value of the fraction because we are dividing both the
numerator and the denominator by the same thing. 8 divided by 2 is 4, 10 divided
by 2 is 5, and we're done. 0.8 is the same thing as 8/10,
which is the same thing as 4/5.