I assume commas are decimal points and ":" means division. Interpreting the expression that way:

(-20,47:(-8,9)+24,6(-0,5)):0,1
= ((-20.47 / -8.9) + 24.6 (-0.5)) / 0.1

Compute stepwise:
-20.47 / -8.9 = 2.3
24.6 * (-0.5) = -12.3
2.3 + (-12.3) = -10.0
-10.0 / 0.1 = -100

Result: -100

If you meant different notation (e.g. commas as separators or ":" something else), tell me and I’ll recompute.