Question 1095402
<br>You can make solving this easy if you use the fact that if the same distance is covered at two different rates that are in the ratio m:n, then the amounts of time spent at those respective rates are in the ratio n:m.<br>
The total travel time was 3.5 hours.  The ratio of the speeds was 30:40 = 3:4; the ratio of times had to be 4:3.<br>
A bit of arithmetic shows that 3.5 hours divided into two parts in the ratio 4:3 means 2 hours at the first rate and 1.5 hours at the second rate.<br>
Then the distance from A to B can be found using the time and rate for either part of the trip:
2 hours @ 30mph = 60 miles
1.5 hours @ 40mph = 60 miles