Jason is a crystal miner, he has mine some crystals.  He sold 10 more than half of his crystals to Yvonne.  Then, he mined 20 more crystals in Singapore. After that he sell 14 crystals to Cherlyn. He has 35 crystals in the end.  How may crystals he had at first? 
Overseas Competition->Knowledge Point->Word Problem Modules->Inverse Operation Problems