20道混合运算
9/7-(2/7–10/21)5/9×18–14×2/74/5×25/16+2/3×3/414×8/7–5/6×12/1517/32–3/4×9/243×2/9+1/35/7×3/25+3/73/14××2/3+1/61/5×2/3+5/69/22+1/...