\frac{dx_{1}}{dt} = \left(1 \cdot k_{21} \cdot k_{6} + -1 \cdot k_{21} \cdot k_{7} \cdot x_{1} + -1 \cdot k_{21} \cdot k_{8} \cdot x_{5} \cdot x_{1} + -1 \cdot k_{21} \cdot k_{9} \cdot x_{5} \cdot x_{1}\right) / k_{21}\\ \frac{dx_{2}}{dt} = \left(1 \cdot k_{21} \cdot k_{8} \cdot x_{5} \cdot x_{1} + -1 \cdot k_{21} \cdot k_{2} \cdot x_{2} + -1 \cdot k_{21} \cdot k_{12} \cdot x_{2} + 1 \cdot k_{21} \cdot k_{11} \cdot x_{4} + -1 \cdot k_{21} \cdot k_{13} \cdot x_{6} \cdot x_{2} + -1 \cdot k_{21} \cdot k_{17} \cdot x_{16} \cdot x_{2}\right) / k_{21}\\ \frac{dx_{3}}{dt} = \left(1 \cdot k_{21} \cdot k_{12} \cdot x_{2} + -1 \cdot k_{21} \cdot k_{3} \cdot x_{3} + -1 \cdot k_{21} \cdot k_{13} \cdot x_{6} \cdot x_{3} + -1 \cdot k_{21} \cdot k_{17} \cdot x_{16} \cdot x_{3}\right) / k_{21}\\ \frac{dx_{4}}{dt} = \left(1 \cdot k_{21} \cdot k_{9} \cdot x_{5} \cdot x_{1} + -1 \cdot k_{21} \cdot k_{11} \cdot x_{4} + -1 \cdot k_{21} \cdot k_{7} \cdot x_{4}\right) / k_{21}\\ \frac{dx_{5}}{dt} = \left(1 \cdot k_{21} \cdot k_{4} \cdot x_{3} + -1 \cdot k_{21} \cdot k_{5} \cdot x_{5}\right) / k_{21}\\ \frac{dx_{6}}{dt} = \left(1 \cdot k_{21} \cdot k_{10} \cdot x_{15} + 1 \cdot k_{21} \cdot k_{14} \cdot \left(x_{2} + x_{3}\right) \cdot x_{6} + -1 \cdot k_{21} \cdot k_{16} \cdot x_{6}\right) / k_{21}\\ \frac{dx_{7}}{dt} = -1 \cdot k_{21} \cdot k_{15} \cdot x_{7} / k_{21}\\ \frac{dx_{8}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{7} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{8}\right) / k_{21}\\ \frac{dx_{9}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{8} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{9}\right) / k_{21}\\ \frac{dx_{10}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{9} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{10}\right) / k_{21}\\ \frac{dx_{11}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{10} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{11}\right) / k_{21}\\ \frac{dx_{12}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{11} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{12}\right) / k_{21}\\ \frac{dx_{13}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{12} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{13}\right) / k_{21}\\ \frac{dx_{14}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{13} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{14}\right) / k_{21}\\ \frac{dx_{15}}{dt} = \left(2 \cdot k_{21} \cdot k_{15} \cdot x_{14} + -1 \cdot k_{21} \cdot k_{15} \cdot x_{15}\right) / k_{21}\\ \frac{dx_{16}}{dt} = \left(1 \cdot k_{21} \cdot k_{20} + 1 \cdot k_{21} \cdot k_{18} \cdot \left(x_{2} + x_{3}\right) \cdot x_{16} + -1 \cdot k_{21} \cdot k_{19} \cdot x_{16}\right) / k_{21}