Hi All, ia m actually trying the below trail head ...
-------------------------------------
Keep contact addresses in sync with their account's address
You've been given a requirement to keep contact addresses in sync with the accounts they belong to. Use Process Builder to create a process on the Account object that updates child Contact addresses when an account's address is updated.

Challenge Requirements:
The process can have any name
The process must have an Update Records action that updates Contact mailing address fields (Street, City, State, Postal Code, Country) when the parent Account shipping address field values are updated
The process must be active

NOTE: To complete this challenge, you may have to deactivate the validation rule for the Account object (created from a previous challenge).-------------------------------------------------------------

1. for this is selected the account obj and action while creating and editing.
2. in criteria i entered the formula as below 
OR(

ISCHANGED([Account].ShippingStreet),

ISCHANGED([Account].ShippingCity)  ,

ISCHANGED([Account].ShippingState),

ISCHANGED([Account].ShippingCountry),

ISCHANGED([Account].ShippingPostalCode)

) 

3. immediate change : No criteria—just update the records!

Field                          *Type*                 Value*

1.Mailing Street      Field refrence   [Account].Shipping address
2. similarly for all other Street, City, State, Postal Code, Country as per requirement 

then activated it ...

getting below error while selecting check challenge in trial head 
There was an unexpected error in your org which is preventing this assessment check from completing: System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Account number must be 8 characters long.: []

pls comfirm me is my logic correct