b) $\left(+\frac{2}{3}\right)^{9}:\left(+\frac{2}{3}\right)^{5}$

Step 1 ：Rewrite the expression as \(\left(+\frac{2}{3}\right)^{9-5}\)

Step 2 ：Calculate the exponent: \(9-5=4\)

Step 3 ：Compute the final answer: \(\left(+\frac{2}{3}\right)^{4} \approx 0.1975\)

Step 4 ：\(\boxed{0.1975}\)