BLAINE, Wash. (AP) — This is why math is important.



The co-owner of a Blaine, Washington, marijuana store says a simple math error caused an employee to sell pot to a minor during a state compliance check.



The Bellingham Herald reports the violation means Evergreen Cannabis will face a 10-day suspension or a $2,500 fine from the state Liquor Control Board.



Co-owner and manager Jacob Lamont says the customer's identification showed a birth date only a couple months shy of 21. He says the employee "did her own math, and that was the problem." Lamont says the store has been making changes to prevent such mistakes in the future.



As Lamont puts it, "It's not like I hire really shady people, it's just that they're human."



The Liquor Control Board said Thursday that in its first complete round of retail marijuana store compliance checks, 18 out of 157 stores sold marijuana to an underage investigative aide. One store sold to a minor twice, making a total of 19 violations.