Ask.com is my default Google Chrome home page or search engine in Windows. How do I change it?

To do this, click on the Tools menu from the button with either three horizontal lines or three vertical dots in the upper right corner of the the Google Chrome browser, and then click on "Settings" from the drop down menu. 

Scroll all the way to the bottom of the Settings tab, will indicate your current setting for your homepage (titled “On Startup”) and your default search provider (titled “Search engine”). Use the corresponding drop-down menu at "Search engine" to change your default search provider, and choose the first option under "On Startup" to see Google Chrome's default new tab.

 If Ask is currently set as your homepage or default search provider, you must disable the Ask extension in order to change the setting. Chrome will display an option to disable the extension as shown below. You can click on the "Disable Extension" button and then set your desired homepage or search provider. In some cases, you may have separate Ask extensions installed for your homepage and default search provider settings, and you may need to disable them separately.

If you want to remove the Ask New Tab page, please follow these instructions on how to remove the extension from Chrome.