To create a histogram on the Quantity field by using bin size of 3, you need to do the following steps:

Open the link to Book1 found on the desktop. This will open the Tableau workbook that uses the Superstore data source.

Click on the Histogram tab at the bottom of the workbook to open the Histogram worksheet. You will see a blank worksheet with no marks.

Right-click on Quantity in the Measures pane and select Create Bins from the menu. This will open a dialog box that allows you to create bins for the Quantity field. Bins are groups of values that are treated as one unit in a histogram.

Enter 3 in the Size of bins text box. This will set the bin size to 3, which means that each bin will contain values that are 3 units apart. For example, one bin will contain values from 0 to 2, another bin will contain values from 3 to 5, and so on.

Click OK to create the bins. You will see a new field named Quantity (bin) in the Measures pane with a # sign next to it.

Drag Quantity (bin) from the Measures pane to Columns on the worksheet. This will create a histogram that shows the distribution of Quantity by bins. You will see bars that represent the frequency or count of values in each bin.

Optionally, you can adjust the width, color, and labels of the bars by using the options on the Marks card. You can also add filters, tooltips, or annotations to enhance your histogram.

Using relationships: You can use relationships to link the secondary data source with the primary data source based on a common field. This will allow you to use fields from both data sources in your visualization without creating new fields or duplicating data. You can then replace references to update the dimension values. For example, you can use relationships to link the updated dorm codes with the primary data source and then replace Dorm_Code with Dorm_Code_New in your visualization.

https://community.tableau.com/s/question/0D54T00000C5ldZSAR/update-data-view-based-on-dimension

To modify the bar chart to show the percentage of sales for each Subcategory within every Category, you need to do the following steps:

Open the link to Book1 found on the desktop. This will open the Tableau workbook that contains the CategoryPercentage worksheet.

Click on the CategoryPercentage tab at the bottom of the workbook to open the worksheet. You will see a bar chart that shows the total sales for each Subcategory across all Categories.

Right-click on Sales on the Columns shelf and select Add Table Calculation from the menu. This will open a dialog box that allows you to apply a calculation to your measure.

Select Percent of Total from the Calculation Type drop-down list. This will calculate the percentage of sales for each Subcategory out of the total sales for all Subcategories.

Select Category from the Compute Using drop-down list. This will calculate the percentage of sales for each Subcategory within every Category, instead of across all Categories. The total percentage for every Category will be 100%.

Click OK to apply the table calculation. You will see that the bar chart now shows the percentage of sales for each Subcategory within every Category.

To analyze the average revenue per product in different regions over time, you need to use two fields that contain numeric, quantitative values that you can measure and aggregate. Quantity and Revenue are both measures that fit this criterion. You can multiply Quantity and Revenue to get the total sales for each product, and then divide by the number of products to get the average revenue. You can also use these measures to create charts and tables that show the trends and comparisons over time and across regions.Reference:

Dimensions and Measures, Blue and Green - Tableau

Tableau Certified Data Analyst Study Guide