Wash. Rev. Code § 9.46.0305
The legislature hereby authorizes the wagering on the outcome of the roll of dice or the flipping of or matching of coins on the premises of an establishment engaged in the business of selling food or beverages for consumption on the premises to determine which of the participants will pay for coin-operated music on the premises or certain items of food or beverages served or sold by such establishment and therein consumed. Such establishments are hereby authorized to possess dice and dice cups on their premises, but only for use in such limited wagering. Persons engaged in such limited form of wagering shall not be subject to the criminal or civil penalties otherwise provided for in this chapter.
RCW 9.46.0305
Minors barred from gambling activities: RCW 9.46.228.