Rep. Ed Markey was trying to explain why the Keystone XL Pipeline shouldn’t be completed.

He’s wrong about that, but that’s a different editorial.

Last week, the Massachusetts Democrat was debating Republican Gabriel Gomez, a former Navy SEAL and his opponent in the June 25 special election to choose a replacement for John Kerry, who left the Senate this year to become Secretary of State.

Rep. Markey, playing a numbers game on the Keystone issue: “It’s really not math. It’s just arithmetic. It’s very simple arithmetic. It’s not as complicated as math.”

Ridicule ensued from assorted conservative outposts about what dailycaller.com called Rep. Markey’s “somewhat confusing remark.”

Yet according to merriam-webster.com, arithmetic really isn’t always as complicated as math.

That online dictionary’s first definitions of those words:

“arithmetic: a branch of mathematics that deals usually with the nonnegative real numbers including sometimes the transfinite cardinals and with the application of the operations of addition, subtraction, multiplication, and division to them.”

“math: the science of numbers and their operations, interrelations, combinations, generalizations, and abstractions and of space configurations and their structure, measurement, transformations, and generalizations.”

And now that Rep. Markey’s grasp of that defining distinction has been confirmed, he should reflect on this alarming, persisting math problem:

The federal budget — and national debt — have soared since he was first elected to Congress.

That was back in 1976, when the budget was $372 billion and the national debt was $620 billion.

This year, the budget is $3.8 trillion, and as of today, the national debt is $16.75 trillion.

Do the math.