Traveling Through Prehistoric Times: Teaching Disciples and Getting Back Hundreds of Millions of Times

The protagonist Tang Xuan dies unexpectedly and travels to another world. I thought I would be reincarnated as an innate god and demon, but I didn't expect to be reincarnated into a dragon clan that declined after the Dragon and Phoenix Tribulation, and a mixed-blood dragon clan. Fortunately, there is a system in which teachers and apprentices will get double the money back. Let's see how he relies on his own calculations and the magic of the system to seize chestnuts from the fire, prove the transcendent path, become famous in the world, and shock the world.