Answer:
87.5π units.
Explanation:
First off, you need to find the area of the entire circle.
The formula for that is πr^2. In this case, it is π * 15^2, which is 225π.
Then, you can set up a proportion to find the area of the shaded sector.

This means that the area of the sector over the degrees of the angle equals the area of the circle over the degrees of the circle.
That results in...
360x = 140 * 225π
360x = 31500π
36x = 3150π
x = 87.5π
And that's your area!
Hope this helps!