To solve this equation, we first need to convert the mixed numbers into improper fractions:

13 3/4 = 55/4
12 13/14 = 181/14

Now we substitute these values into the equation:

2,4 + 5,6 * (55/4 - 181/14)

Next, we simplify the expression inside the parentheses:

55/4 - 181/14
= (557 - 1814)/(4*7)
= (385 - 724)/28
= -339/28

Substitute this back into the equation:

2.4 + 5.6 * (-339/28)

Now we multiply the outer term:

5.6 * (-339/28)
= -1900.4/28
= -67.8714285714

Finally, add the remaining terms:

2.4 - 67.8714285714
= -65.4714285714

Therefore, the result of the expression 2,4 + 5,6 * (13 3/4 - 12 13/14) is approximately -65.47.