To solve these expressions, we need to simplify each one step by step.

(3/4 + 1/2):

First, find a common denominator for 4 and 2, which is 4. Then, rewrite the expression with the common denominator:

(3/4 + 2/4) = 5/4

Therefore, the answer is 5/4.

(3/5 - 12/25) / 4/5:

First, find a common denominator for 5 and 25, which is 25. Then, rewrite the expression with the common denominator:

(15/25 - 12/25) / 4/5 = 3/25 / 4/5

Next, divide the fractions by multiplying by the reciprocal of the second fraction:

(3/25) x (5/4) = 15/100 = 3/20

Therefore, the answer is 3/20.

4/15 / (1 1/5 - 2/3):

Convert the mixed number 1 1/5 to an improper fraction.

1 1/5 = 6/5

Now we have:

4/15 / (6/5 - 2/3) = 4/15 / (18/15 - 10/15) = 4/15 / 8/15

Next, divide the fractions by multiplying by the reciprocal of the second fraction:

(4/15) x (15/8) = 60/120 = 1/2

Therefore, the answer is 1/2.