A) -3/8 + 5/6

To add these fractions, we need to have a common denominator. The least common multiple of 8 and 6 is 24.

-3/8 = -9/24
5/6 = 20/24

Now, we can add the fractions:

-9/24 + 20/24 = (20 - 9) / 24 = 11/24

So, -3/8 + 5/6 = 11/24

B) -3 5/9 - 2 7/18

To subtract these mixed numbers, we need to convert them to improper fractions first.

-3 5/9 = -3 9 + 5 / 9 = -27 + 5 / 9 = -22/9
-2 7/18 = -2 18 + 7 / 18 = -36 + 7 / 18 = -29/18

Now, we can subtract the improper fractions:

-22/9 - 29/18

To subtract fractions we need a common denominator. The least common multiple of 9 and 18 is 18.

-22/9 = -44/18
-29/18 = -29/18

Now, we can subtract the fractions:

-44/18 - 29/18 = (-44 - 29) / 18 = -73/18

Therefore, -3 5/9 - 2 7/18 = -73/18.