Answer:
The solution to the question will be explained better using the image below
Concept:
The formula to calculate momentum is given below as
![\begin{gathered} momentum=mass* velocity \\ m=mv \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/mkw599onabt8ggv0602er7bj7bwogk81mh.png)
The first momentum will be
![\begin{gathered} m_1=m_1v_1 \\ m_1=6*13 \\ m_1=78kg\text{ m/s} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/w7odbmgthm7i8u03se2f5vsfhmjg6c1rqr.png)
The second momentum will be
![\begin{gathered} m_2=m_2v_2 \\ m_2=14kg*7 \\ m_2=98kg\text{ m/s} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/rri5tv2ex7np5gfexxnmozfeq1kgfc0k9n.png)
Since they are moving in different directions,
We will substract both momentums
![\begin{gathered} momentum=m_1v_1-m_2v_2 \\ momentum=78-98 \\ momentum=-20kg\text{ m/s} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/uvc63mn7x7w67ci5n759e78vz64bja48nf.png)
Hence,
The momentum of a system that consists of two objects should be 20 kg m/s in the direction of the negative x-axis