Answer:
11 miles per day
Step-by-step explanation:
To complete 80 miles, Marcus needs to bike an additional ...
80 -25 = 55 . . . miles
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If he divides that evenly among the 5 remaining days, he needs to bike ...
(55 mi)/(5 day) = 11 mi/day
Marcus should bike 11 miles on each of the 5 remaining days.