I have absolutely no clue how mile markers work, but assuming they mark a single mile each, his sister will either be five miles in front, or five miles behind him.
The possible answers are mile markers 8 and 18.
Let's say that you're in your room and you find that the current temperature of 72 degrees is too cold, so slowly you increase the temperature of the room by two degrees.
We know that the explicit formula is
a^n=a^1+ (n-1)d
and so by substituting the given information in
a^n= 72 + (n-1)2
a^1=Initial temp
d= rate of change
by substitution a value of n (the term we are looking for) into this equation, you can then calculate the temperature that you just set the room too.
6
84
91
395
All these are rounded to the nearest whole number
