hello
since this question request we solve for the explicit formula, we are going to assume that the sequence is an arithmetic progression and the formula of explicit formula is given as
[tex]\begin{gathered} f(n)=a+(n-1)d \\ a=\text{ first term } \\ n=\text{nth term} \\ d=common\text{ difference} \end{gathered}[/tex]in this case, we can define our values as
[tex]\begin{gathered} a=200 \\ d=25 \\ n=n \end{gathered}[/tex][tex]\begin{gathered} f(n)=200+(n-1)25 \\ n=\text{ number of days} \end{gathered}[/tex]