M = (3+ 1/417).1/762 - 1/139(4 +761/762) - 4/417.762 + 5/139
= 3/762 + 1/417.762 - 4/139 - 761/139.762 - 4/417.762 + 5/139
= 3/762 - 3/417.762 + 1/139 - 761/139.762 =
= 1179/ 139.762 - 761/139.762 - 3/417.762 =
= 418/139.762 - 3/417.762 =418/139.762 - 1/139.762 = 417/139.762 = 3/762 = 1/254