To solve this expression, we need to follow the order of operations (PEMDAS):

1. Parentheses: There are no parentheses in this expression.
2. Exponents: There are no exponents in this expression.
3. Multiplication and Division: We have one division operation, 15/30, which simplifies to 1/2. We also have a fraction, 5/6, which we need to convert to a decimal by dividing 5 by 6: 5/6 = 0.8333. Finally, we have a mixed number, 4 2/3, which we need to convert to an improper fraction: 4 2/3 = (4 x 3 + 2) / 3 = 14/3. So, the expression becomes:

1,25 : 1/2 + (25% - 0.8333) : 14/3

4. Addition and Subtraction: We have one subtraction operation, 25% - 0.8333, which we can convert to a decimal by dividing 25 by 100 and then subtracting 0.8333: 0.25 - 0.8333 = -0.5833. We also have one addition operation, 1,25 : 1/2 + (-0.5833) : 14/3, which we can simplify by finding a common denominator for the fractions:

1,25 : 1/2 + (-0.5833) : 14/3 = 2,5 : 1 + (-0.5833 x 2) : (14/3 x 2) = 2,5 + (-1.1666) : 7 = 2,5 - 0.1666 = 2.3334

Therefore, the final answer is 2.3334.