A circular path 2feet wide has an inner diameter of 150 feet. How much farther is it around the outer edge of the path than around the inner edge?

The circumference of any circle is

diameter x pi.

Distance around the outside of the walk is (150+2+2) pi = 154 pi feet.

Distance around the inside of the walk is 150 pi feet.

Difference = 4 pi feet.

Same as if you strung a string around the Earth that was 2 feet off the surface everywhere.

The string would be 4pi feet longer than the Earth's circumference at the surface ... about 12.5 feet.