(1) 2 3/4 - 1 5/6
First, convert both fractions to have a common denominator.
2 3/4 = 2 18/12
1 5/6 = 1 10/12

2 18/12 - 1 10/12
= 2 - 1 + 18/12 - 10/12
= 1 + 8/12
= 1 2/3

(2) 4 2/5 + 3 5/6
First, convert both fractions to have a common denominator.
4 2/5 = 4 24/30
3 5/6 = 3 25/30

4 24/30 + 3 25/30
= 4 + 3 + 24/30 + 25/30
= 7 + 49/30
= 7 19/30

(3) 7 5/12 - (1 5/8 + 2 1/24)
First, convert the inner brackets to have a common denominator.
1 5/8 = 1 15/24

7 5/12 - (1 15/24 + 2 1/24)
= 7 5/12 - 1 15/24 - 2 1/24
= 7 5/12 - 1 15/24 - 2 1/24
= 7 5/12 - 1 15/24 - 2 1/24

Now, convert the top equation to make the common denominator
7 5/12 - 1 15/24 - 2 1/24
= 7 10/24 - 1 15/24 - 2 1/24
= 7 - 1 - 2 + 10/24 - 15/24 - 1/24
= 4 - 6/24
= 4 - 1/4
= 3 3/4