Question

See attachment.

Answer 1

I got Distance = 660 miles
Speed = x miles/hr
Time taken = 660/x

Now, if Speed was x+5, time would have been 660/x - 1
So, we have:
660/(x+5) = 660/x - 1
660/(x+5) = (660-x)/x
x=-60,55

Answer 2

is that right?

Answer 3

yes! Now just remember that a negative answer is impossible, and use only the positive one.

Answer 4

The formula you came up with is exactly right.

Answer 5

You can now verify that 55 miles per hour, driving 660 miles would have taken 12 hours. With 55+5 (x+5) miles per hour, you can drive that distance in 11 hours (one hour less). So, the answer is good!