today I read cnbc magazine and they asked why shares are not 190$ when IBM is paying premium price of 190 but now are 170, one of the reason was that China has not still approve the deal. I am not sure why China has to approve this deal ?
China approved new antitrust laws in 2008. There are always variations in the details from jurisdiction to jurisdiction, but China's Anti-Monopoly Law shares the key features of its counterparts in most other major economies. Therefore, in addition to prohibitions on the abuse of monopoly power, and prohibitions on price-fixing, it also requires businesses to request and receive government approval before moving forward with acquisitions of a certain size.
This requirement applies to any transaction involving companies with at least ~$63 million in annual sales in China, so the IBM-Red Hat deal would easily trigger review by the Ministry of Commerce.