So:
[tex]5x+25\ge80[/tex]Solving the inequality:
[tex]\begin{gathered} \text{Subtract 25 from both sides:} \\ 5x\ge80-25 \\ 5x\ge55 \\ \text{divide both sides by 5:} \\ x\ge\frac{55}{5} \\ x\ge11 \end{gathered}[/tex]Therefore he should bike at least 11 miles on each of the 5 remaining days