Nike Inc. shares gained on third-quarter net income that rose 55 percent as the athletic gear maker’s resurgence in North America and easing material costs helped offset continued weakness in China. Nike has been dealing with Europe’s fluctuating economy and a slowdown in growth in China. The company has reduced its inventory in China and reworked its offerings. It also has focused on growth in North America, selling off less profitable brands such as Umbro. North American revenue rose 18 percent to $2.55 billion.