(I appreciate I'm something or a bore harping on about Trûmp and his failure to understand basic maths and %ages but I can't believe or understand how a (self-)acclaimed businessman can get anywhere without being able to work out basic %ages, beggars belief and either maybe he wasn't the business success he declares or maybe well progressed along age related cognitive decline or probably both?).
If you are very rich, you employ other people to do that stuff.
He got $413 million from his dad. He was very good at setting up sham organisations to dodge taxes. It's estimated that Fred and Mary Trump dodged about $500m in taxes.
Trump's next wheeze was just to make up his net worth and overvalue assets to get loans and secure deals. The only real money he ever made was through the Apprentice. Everything else has been dodgy. His current wealth is the result of insider trading and from "donations" for favours or because he knows where bodies are buried. He was happy to be used by people as long as they stroked his ego and gave him money. An easy way for people to legitimise their own dodgy dealings.