Who tipped off Hank in 3:7

Its never actually explained who placed the call, but during a conversation between Gus and Walt Walt implies that he believes that Gus was responsible for the call as part of a strategy to make the DEA apply more pressure against the cartel and as a result, cutting off the supply of meth from Mexico so Gus would be free to exclusively distribute his own product and no longer have to distribute Mexico's meth. As Walt says, killing two birds with one stone.

Gus neither confirms nor denies walts theory, but its fairly obvious it was placed by Gus or someone from Gus's camp.

Personally I suspect it was Mike. Its possible Mike was tailing the twins and knew when they were at the DEA office, and how far they were from approaching hank in the parking lot.

That makes sense. Thank you!!

It was Gus. Gus hated the Cartels. Maybe he had someone do it for him but it was Gus who had the control over it