1) 5/7*(21/20-7)+16/21: 8/7 2) 4/45: (12/25-4/15)+15/16*4/15

5/7 * (21/20 - 7/30) + 16/21 : 8/7 = 1 1/4
1) 21/20 - 7/30 = 63/60 - 14/60 = 49/60
2) 5/7 * 49/60 = (1*7)/(1*12) = 7/12
3) 16/21 : 8/7 = 16/21 * 7/8 = (2*1)/(3*1) = 2/3
4) 7/12 + 2/3 = 7/12 + 8/12 = 15/12 = 1 3/12 = 1 1/4

4/45 : (12/25 - 4/15) + 15/16 * 4/15 = 2/3
1) 12/25 - 4/15 = 36/75 - 20/75 = 16/75
2) 4/45 : 16/75 = 4/45 * 75/16 = (1*15)/(9*4) = 15/36 = 5/12
3) 15/16 * 4/15 = 4/16 = 1/4
4) 5/12 + 1/4 = 5/12 + 3/12 = 8/12 = 2/3