Сделаем вычисления поочередно:

5(4/45) - 4(1/6) = 229/45 - 25/6 = 458/90 - 375/90 = 83/90

83/90 : 5(8/15) = 83/90 : 83/15 = 83/90 * 15/83 = 1/6

4(2/3) + 0,75 = 14/3 + 75/100 = 14/3 + 3/4 = 65/12

65/12 * 3(9/13) = 65/12 * 48/13 = 20

20 * 34(2/7) = 20 * 240/7 = 4800/7

0,3 : 0,01 = 3/10 : 1/100 = 3/10 * 100 = 30

30/70 = 3/7

4800/7 + 3/7 = 4803/7

4803/7 + 2/7 = 4805/7 = 686(3/7)