209/20÷【7又36分之15*17/5）*1.8-0.625*13/6】=209/20÷【7又36分之15*1.8*17/5-0.625*13/6】=209/20÷【13.35*17/5-5/8*13/6】=209/20÷【45.39-65/48】=209/20÷54043/1200=1254/54043