8 and a half plus 1 and 2 sixths

is your problem

You need to convert the denominators so that they are the same

But aside the whole numbers for now so get  and multiply both sides by 3 so that it is 

Now get the mixed fractions and add them

+ 

 

First write out the problem, 
8 1/2-1 2/6
Next find a common denominator, because 2 goes into 6, 3 times are common denominator is going to be 6.
So now we take 1*3=3 and 2*3=6 = 8 3/6 
Now Add
8 3/6+1 2/6=9 5/6
Giving us are end answer of 9 5/6