Clone the circle (Ctrl K), and reduce the cloned circle to 160 pixels. The easy way to do this is to type in 160 in the Width or Height text entry box on the Infobar, making sure that the padlock button is on. Press Enter to apply the change.
If they are not already centered, center the star and two circles.
Select the smaller circle, Shift-select the star, and then Combine Shapes... Intersect Shapes ( Ctrl 3).
