\( \frac{-2}{5}, \frac{2}{3}, \frac{7}{15} \), 20. Solve \( :\left\{\left(3^{3}\right)^{2} \times 3^{3} \div 3^{7}\right\}+3^{0} \)

First, let’s simplify the expression step by step. Start with the nested expression: \((3^3)^2\) simplifies to \(3^{3 \times 2} = 3^6\). Now substitute back into the original equation: \[ \left\{3^6 \times 3^3 \div 3^7\right\} \] Using the laws of exponents, we can combine the multiplication first: \(3^6 \times 3^3 = 3^{6 + 3} = 3^9\). Next, divide by \(3^7\): \[ 3^9 \div 3^7 = 3^{9 - 7} = 3^2 \] Now, simplify \(3^2 = 9\). Don't forget about the \(+3^0\), which equals \(1\): So, we add: \[9 + 1 = 10.\] The final answer is: \[ \boxed{10}. \]