Explanation
The following options are available in the Device preview section when creating a Dashboard:

Explanation
The following showcase how you can show mark labels. Using the Sample Superstore dataset:
1) Let's create a Bar chart showing the sales for each sub-category:

2) Now you can show labels by:
2.1) Click on Show Mark Labels Icon in the Toolbar ( easiest )



2.2) Drag Sales to the Text icon in the Marks Card:
2.3) Click on Analysis -> Show mark labels from the Tableau menu bar:

Explanation
To make an axis bold, simply right click it, select format, and then click on Font to choose Bold:

None of the other options are valid ways to make the axis bold.

Read more about editing axis: https://help.tableau.com/current/pro/desktop/en-us/formatting_editaxes.htm

Explanation
You can use Wildcard Search to set up search criteria to automatically include tables in your union. Use the wildcard character, which is an asterisk (*), to match a sequence or pattern of characters in the Excel workbook and worksheet names, Google Sheets workbook and worksheet names, text file names, JSON file names, .pdf file names, and database table names.
When working with Excel, text file data, JSON file, .pdf file data, you can also use this method to union files across folders, and worksheets across workbooks. Search is scoped to the selected connection. The connection and the tables available in a connection are shown on the left pane of the Data source page.

Explanation
We need to use the concept of Groups for this question. Follow along:
1) First, Drag State to the Rows shelf, and Total Expenses to the Text Mark on the Marks Shelf:

2) Now, remove the SUM aggregation from Total Expenses, and add a quick table calculation -> Percent of total:

3) Next, Select the States of New York, California and Washington -> And then click the paperclip icon:

We can see the answer already : 23.386% in the view above (even before grouping!)
4) Finally, we get the following view and our answer: