Stephen Colbert thinks he knows why the White House executive budget features a two-trillion-dollar mathematical error. “There’s a simple explanation for how this happened: Donald Trump is an idiot. Or he’s lying.”

Reviewing the “logic” behind Trump’s budget math, Colbert notes that cutting rich people’s taxes is expected to “magically” increase revenues by two trillion bucks over ten years — and that budget director Mick Mulvaney then doubles the magic by counting that revenue twice. Magically, a two trillion dollars increase in tax revenues from economic growth when we cut rich people’s taxes…and then counts that revenue twice,

“That’s like robbing Peter to pay Paul,” he snarks, “but you’re paying Paul with a Blockbuster gift certificate…that doesn’t work any more.”

Trying to help Trump, Stephen offers a special introductory math problem — with an uplifting solution.