Answer:
a. 125 – 7d
Step-by-step explanation:
Let d be the number of days.
<u>Given the following data;</u>
Total distance (month) = 125 miles
Distance covered per day = 7 miles
To determine how many miles he has left to run after running for "d" days, this mathematical expression can be used;
Total distance - distance covered per day = number of miles remaining