\frac{dx_{1}}{dt} = \left(-1 \cdot \left(k_{1} \cdot k_{16} \cdot x_{1} + k_{2} \cdot x_{1}\right) + 1 \cdot k_{3} \cdot x_{2} + 1 \cdot k_{8} \cdot x_{3} + 1 \cdot k_{9} \cdot x_{5}\right) / k_{20}\\
\frac{dx_{2}}{dt} = \left(1 \cdot \left(k_{1} \cdot k_{16} \cdot x_{1} + k_{2} \cdot x_{1}\right) + -1 \cdot k_{3} \cdot x_{2} + -1 \cdot k_{4} \cdot x_{2}\right) / k_{20}\\
\frac{dx_{3}}{dt} = \left(1 \cdot k_{4} \cdot x_{2} + -1 \cdot k_{5} \cdot x_{3} + -1 \cdot k_{8} \cdot x_{3}\right) / k_{20}\\
\frac{dx_{4}}{dt} = \left(1 \cdot k_{5} \cdot x_{3} + -1 \cdot x_{4} \cdot \left(k_{6} + k_{7} \cdot x_{9} / \left(1 + x_{9}\right)\right)\right) / k_{20}\\
\frac{dx_{5}}{dt} = \left(1 \cdot x_{4} \cdot \left(k_{6} + k_{7} \cdot x_{9} / \left(1 + x_{9}\right)\right) + -1 \cdot k_{9} \cdot x_{5}\right) / k_{20}\\
\frac{dx_{6}}{dt} = \left(-1 \cdot k_{10} \cdot x_{6} \cdot \left(x_{3} + k_{11} \cdot x_{4}\right) / \left(1 + k_{13} \cdot x_{9}\right) + 1 \cdot k_{12} \cdot x_{7}\right) / k_{20}\\
\frac{dx_{7}}{dt} = \left(1 \cdot k_{10} \cdot x_{6} \cdot \left(x_{3} + k_{11} \cdot x_{4}\right) / \left(1 + k_{13} \cdot x_{9}\right) + -1 \cdot k_{12} \cdot x_{7}\right) / k_{20}\\
\frac{dx_{8}}{dt} = \left(-1 \cdot k_{14} \cdot x_{8} \cdot x_{7} + 1 \cdot k_{15} \cdot x_{9}\right) / k_{20}\\
\frac{dx_{9}}{dt} = \left(1 \cdot k_{14} \cdot x_{8} \cdot x_{7} + -1 \cdot k_{15} \cdot x_{9}\right) / k_{20}