Question 1102816
.
You may interpret the condition in this way:


<pre>
    The entire distance can be represented as some number of equal pieces each of the length 31 = 30 + 1 miles.
</pre>


Now, &nbsp;how many such pieces are there in &nbsp;651 miles ?  &nbsp;&nbsp;- It is not difficult to answer: &nbsp;&nbsp;{{{651/31}}} = 21.


Therefore, &nbsp;Dana just covered &nbsp;21*30 = 630 miles, &nbsp;and she has left to drive &nbsp;21 mile.


You may check that  &nbsp;21*30 + 21*1 = 651,  exactly as the condition states.



<U>Solved</U>.