You can
put this solution on YOUR website!The problem is really asking:
What is the difference in the radii of two circles, one having a circumference (C1) of 25,000 miles and the other having a circumference (C2) of 25,000 miles + 18 feet.
The circumference (C) of a circle, in terms of the radius (r), is given by:

Rewrite this in terms of r.
For the first circumference (C1=25,000 miles), we can write:

For the expanded circumference (C2=25,000 mi + 18 ft) we can write:
To find the difference (d), we'll subtract r1 from r2.

But

feet
So:

Feet.