14. Вычислите: 13 - (3 - 20/21) : 4/3 + 10

3 - 20/21 = 63/21 - 20/21 = 43/21.
(43/21) : 4/3 = (43/21) * (3/4) = 43/28.
13 - 43/28 + 10 = 23 - 43/28 = (23 * 28 - 43) / 28 = (644 - 43) / 28 = 601/28.