Вычислите: 13-(3-1 20/21):(4/49 + 3/10)

1 20/21 = 41/21

3 - 41/21 = 63/21 - 41/21 = 22/21

4/49 + 3/10 = 40/490 + 147/490 = 187/490

(22/21) : (187/490) = (22/21) * (490/187) = (22 * 490) / (21 * 187) = (2 * 70) / (3 * 17) = 140/51

13 - 140/51 = (13*51 - 140) / 51 = (663 - 140) / 51 = 523/51