Of the many clichéd phrases that repeatedly pop up in articles, the saying "You do the math" is one of the lamest. That's because telling readers to "do the math" is often a lazy way for journalists to pretend that something's obvious—even if the numbers don't mean much. Even if they did, the writer often leaves out essential parts of whatever equation you're supposed to be setting up and solving. In the following recent examples, Gelf will attempt to solve for x:

New York Times
Jim Greer, founder and chief executive of Kongregate, an online game company in San Francisco, said its statistics indicate that peak game times are in the middle of the workday. Mr. Greer said that the site topped out at 800,000 users around 1 p.m. each day, and added that the site registers a significant drop-off in traffic after 5 p.m. Eastern time. "We don’t know for certain that all of those people are at work, but most people work between the hours of 9 a.m. and 5 p.m.," he said. "You do the math."
((9-5)*800,000)/5) = 640,000

ESPN
If the Sonics actually get a new $400 million arena in Seattle, the price tag of the franchise goes up probably as much as 50 percent. If it moves to Oklahoma City and into what was built four years ago for $88 million, the value of the franchise probably goes down. You do the math.
(400S * 1.5) > ((88(S-4)) * .9). Therefore, S > -41.8

Huron Daily Tribune
I’m not saying Tatum Bell has to be Marshall Faulk, but is it too much to ask him to be Tatum Bell? Bell had 14 yards on nine carries, and a long of 12 yards, so you do the math.
(14-12)/(9-1) = .25. Perhaps that is just Tatum being Tatum.

The Guardian
When a major multinational firm such as Procter & Gamble needs to develop a new cleaning product, it sometimes posts its requirements on InnoCentive, rather than relying on in-house researchers. Crucially, it offers a payment for a successful solution. "If they're looking for a new molecule to take red wine off a shirt—well, you do the math," Tapscott says. "They have 9,000 scientists inside their company boundaries, and 1.5m outside their boundaries. And sure enough, there's a retired chemist in London, or a grad student in Taipei, who comes up with a molecule, and they get paid."
1,500,000/9,000 = 166.67. Now what?

Providence Journal
[Multi-System Therapy] costs between $15,000 to $36,000 a year, as compared with $60,000 to $104,000 for a year in a youth facility. MST has better outcomes, including much lower recidivism. You do the math.
I get a range of $24,000 to $89,000. That's anywhere from a Mazda6 to a Mercedes S550.

Palm Beach Post
As I turned the page on the organization’s tax return and read on, I found that PETA employs not one, not two, but three law firms. One was compensated close to $675,000; another almost $406,000 and the third $224,000! You do the math.
Great, some numbers I can work with! That said, I'm not so sure what $1,287,000 has to do with anything.

Houston Chronicle
That role is Joe Kingman, a pro-football star who's also a swingin' bachelor—at least until a daughter (Madison Pettis) he didn't know he had shows up at his door. [Dwayne "The Rock" Johnson], 35, is 6 foot 4. Pettis, 9, is 4 foot 2. Who wins this comic tug-of-war for our hearts? You do the math.
In case you were wondering, the article is about The Rock's most recent movie, The Game Plan. As for the math, I get a 26 year-old, 2 foot 2 midget. Maybe it's Little Man.

Broward Times
So while mean-spirited MoveOn.Org calls Bush and General Petraeus "traitors," they ignore some very telling numbers, such as 2,726 lost on 9/11 and 9,506 deadly terrorist attacks since 9/11, (according to TheReligionofPeace.com). When the numbers of troops reported killed in Iraq is placed besides the numbers of U.S. citizens killed at home, it looks like this: 3,831 killed (27,004 wounded) vs. 48,802 murders from 2002 - 2004. You do the math.