Explanation
Create the Calculated field 'Math Performers':

Drop the Math Performer field to the Rows and drop gender to filter, select 'Men' Drop the Number of Records (if tableau version prior to 2020.2) to the Text Or Drop the Education.csv(Count) (tableau version 2020.2 and after) to the Text Apply 'Percent of Total' Quick table calculation to the field on the Text marks card:

Enable the Summary Card from Show/Hide menu as shown:
Skewness is .42
Graphical user interface, chart Description automatically generated

Explanation
Drop the country field to the view and also to the filter and select Australia.
Drop the State to the detail marks card.
Create the Unique Customer field to the Label.

Your view will look like this:

Northern Territory has the minimum unique customers - 19.

Click on the State/Province list, and select the State. So Tableau will recognize the city as part of the states in the Country/Region United States.

Explanation
Approach 1 - Using Groups
Drop the Customer ID to the Rows.
Add sub-category to the filter and select phone.
Add Order date to the filter and select the year 2014.

Select all the customers and click on paper clip icon to create the group.
So here we got all the customers who have purchased any product in the Phones subcategory in 2014.
Edit the group and select Include other

Clear the filter shelf, and again add Order date to the filter and select 2015.
Drop Sales to the Text.
Add 'Percent of Total' Quick Table Calculation to the Sales field.
Your view will look like this:

Approach 2 - Using LOD
Create a LOD expressions as:

It will return 1 for the customers who have purchased any product in the Phones sub-category in 2014. For others, it will return 0.
Drop this field to the Rows and add Order date to the filter and select the year 2015.