Wash. Rev. Code § 35.13.050
After the filing with the board of county commissioners of a petition or resolution pursuant to RCW 35.13.015 to call an annexation election, pending the hearing under the twenty percent annexation petition under the election method and pending the election to be called thereunder, the board of county commissioners shall not consider any other petition or resolution involving any portion of the territory embraced therein: PROVIDED, That the petition or resolution may be withdrawn or a new petition or resolution embracing other or different boundaries substituted therefor by a majority of the signers thereof, or in the case of a resolution, by the legislative body of the city or town, and the same proceeding shall be taken as in the case of an original petition or resolution.
RCW 35.13.050