You have the following expression:
9 9/35 - 6 8/10
In order to simplify the prevous expression, first convert the mixed number to normal fractions, just as follow:
9 9/35 = 9/1 + 9/35 = (315 + 9)/(35) = 324/35
6 8/10 = 6/1 + 8/10 = (60 + 8)/10 = 68/10 = 34/5
next, subtract the previous result:
324/35 - 34/5
multiply the second fraction by 7/7 to obtain two homogeneus fractions:
(34/5)(7/7) = 238/35
then, you have
324/35 - 34/5
= 324/35 - 238/35
= (324 - 238)/35
= 86/35
Hence, the simplied expression is 86/35