According to the information given in the exercise, you know that he cycled a total of of 16 kilometers by making 4 trips to work.
Let be "d" the total amount of kilometers Mr. Santos will have cycled after 5 trips to work.
Based on the above, you can set up the following proportion:
[tex]\frac{16}{4}=\frac{d}{5}[/tex]Finally, you must solve for the variable "d" in order to find its value. This is:
[tex]\begin{gathered} 4=\frac{d}{5} \\ \\ (4)(5)=d \\ d=20 \end{gathered}[/tex]Therefore, the answer is:
[tex]20\operatorname{km}[/tex]