Найдите произведение: а)9/10×7/8×5/6... б)3/25×5/6×10/9...в)3/8×2/15×20/72...г)17/13×26/51×8/9....д)8×9/16×7/12...е)4/9×9/8×10/17....ж)9/20×5/8×4/15....з)11/36×2/55×18....и)21/22×12×33/56..