a) To simplify the expression, we need to find a common denominator for the fractions involved. In this case, the common denominator is 12.

3/4 - (7/12 + 3/4 + 5/12)

= 3/4 - (7/12 + 9/12 + 5/12)

= 3/4 - 21/12

= 3/4 - 7/4

= (3 - 7)/4

= -4/4

= -1

b) Again, we need to find a common denominator for the fractions involved. In this case, the common denominator is 24.

(1/3 - 5/8) - (3/8 + 2/3 - 7)

= (8/24 - 15/24) - (9/24 + 16/24 - 168/24)

= -7/24 - (-143/24)

= -7/24 + 143/24

= (143 - 7)/24

= 136/24

= 17/3

c) Finding a common denominator for the fractions involved, which is 45.

(7/9 - 2/3 + 1/5) - (1/3 + 11/9 - 6/5)

= (35/45 - 30/45 + 9/45) - (15/45 + 55/45 - 54/45)

= 14/45 - 14/45

= 0

d) Finding a common denominator for the fractions involved, which is 45.

- (-1/3 - 4/5 + 2/9) + (2/3 + 6/5 - 2/9)

= (5/15 - 12/15 + 10/45) + (30/45 + 54/45 - 10/45)

= 3/15 + 74/45

= 1/5 + 74/45

= (9/45 + 74/45)

= 83/45