Detailed Instructions: This task involves creating questions from a given passage that involve some kind of complex reasoning (including numerical reasoning). 
The generated questions must require looking at more than one part of the passage to answer. Try to use a variety of reasoning types in your questions (some of the sample reasoning types are illustrated in the 'positive examples' field) and also have a variety of answer types (spans, numbers, dates). A span is a continuous phrase taken directly from the passage or question. In such questions, the answer spans are recommended to be five words. Questions with answer type "number", are expected to start with "How many". For instance, "How long did an event last?" can be phrased as "How many years did an event last?". To increase diversity, try to create more questions for which the answer will be multiple spans. Please create questions that require AT LEAST 2 arithmetic operations as illustrated in the 'positive examples' field. You are encouraged to try DIFFERENT COMBINATIONS of operations and not just limit to the combinations shown in those examples. The more challenging questions you create, the better it is.
Q: Passage: In the early 2000s, Flash was widely installed on desktop computers, and was commonly used to display interactive web pages, online games, and to playback video and audio content. In 2005, YouTube was founded by former PayPal employees, and it used Flash Player as a means to display compressed video content on the web. Between 2000 and 2010, numerous businesses used Flash-based websites to launch new products, or to create interactive company portals. Notable users include Nike, Hewlett-Packard, Nokia, General Electric, World Wildlife Fund, HBO, Cartoon Network, Disney and Motorola. After Adobe introduced hardware-accelerated 3D for Flash , Flash websites saw a growth of 3D content for product demonstrations and virtual tours. In 2007, YouTube offered videos in HTML5 format to support the iPhone and iPad, which did not support Flash Player. After a controversy with Apple, Adobe stopped developing Flash Player for Mobile, focussing its efforts on Adobe AIR applications and HTML5 animation. In 2015, Google introduced Google Swiffy to convert Flash animation to HTML5, a tool Google would use to automatically convert Flash web ads for mobile devices. In 2015, YouTube switched to HTML5 technology on all devices, however it will preserve the Flash-based video player for older web browsers.
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
How many years after YouTube was created did it offer videos in HTML5 format as opposed to Flash only?