if "other" statement got chosen open textbox in infopath

I got a combo box control in a info path document that I just created, in the combo box I got few options and "other" option too. My goal is that if the user will chose the "other" option it will open a text box he could write in. How do I do it?

Solution

Easy: Just set a rule to a new field which hides the field as long as the dropdown is not set to "other":

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A user can enter data into the new field (textfield) if he selects other in the first field (combo/drodown).