Under assault for what a think tank described as an effort “to reform the basic rules of math,” D.C. Mayor Vincent Gray on Monday sought to bolster support for a package of tax breaks for technology companies as the D.C. Council prepares to consider the proposal Wednesday.

“I am absolutely convinced that at the end of the day, we will have more dollars coming into the city,” Gray said at an event on K Street. “The legislation won’t cost the District any money.”