5 3/10
The rule is to subtract 1 2/10 each time
To figure this out, first look at the whole numbers
8, 7, 6, ___
You can see that your subtracting one to get to the next number.
Now look at the fractions.
9/10, 7/10, 1/2
To figure out the change you want all the fractions to have the same denominator.
1/2 = 5/10
9/10, 7/10, 5/10, ___
You can now also see that 2/10 is being subtracted each term.
Adding the two changes you get 1 + 2/10 = 1 2/10