-11\12 - (-8\9) = -11\12 + 8\9 = - 33\36 + 32\36 = -1\36

-5  3\28 + 4  5\12 = - 143\28 + 53\12 =−429\84+371\84  = - 29\42

-3  7\12 - 2  5\8 = −43\12−21\8 = −86\24−63\24 =−149\24= −6  5\24