D 18 1/2
1) Since 3 7/10 miles is a mixed number let's turn it into an improper fraction, to make our calculations easier:
![3(7)/(10)=(10*3+7)/(10)=(37)/(10)](https://img.qammunity.org/2023/formulas/mathematics/college/1cdc9psc4fm0hbrqrcbil2grqql6yq7ein.png)
2) So, setting a proportion:
37/10 ---------------------1 day
x ----------------------5 days
Cross multiplying:
![\begin{gathered} x=5\cdot(37)/(10) \\ x=(37)/(2) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/8070syvu8bvr9gnmtmrk6mtavrarybw5n9.png)
So the improper fraction is 37/10 in 5 days. As the question requests in Mixed Number, then
37 /2 =18.5
18.5 = 18 + 0.5 Rewriting 0.5 into fractions 1/2
18.5 = 18 1/2
3) Hence, the answer is 18 1/2