Упростим выражение: (b^(21/9)) * b^(-11) / b^(-10) = b^(7/3) * b^(-11) * b^10 = b^(7/3 - 11 + 10) = b^(7/3 - 1) = b^(4/3).
Подставим b = 0.008 = 8/1000 = (2/10)^3 = (1/5)^3.
b^(4/3) = ((1/5)^3)^(4/3) = (1/5)^4 = 1/625.