ahhh thank you - so it’s not necessary to actually do this (1/7 - 1/6) or (1/9 - 1/8).

another way to look at it is you can subtract 1/5 from both A and B. Then, the problem become compare (-1/6 + 1/7 - 1/8 + 1/9) to 0.

You could simplified it further by adding 1/6 and 1/8 to both sides. Since, 1/6 > 1/8 and 1/7 > 1/9 it must be true that 1/6+1/8 > 1/7 + 1/9

The answer is A.

Not required, just take the sense that substraction will be negative because 1/7 < 1/6 and likewise for other set of numbers.