1. 2/3 : (4/9 - 2/3 * 3/7) = 4,2
1) 2/3 * 3/7 = 2/7
2) 4/9 - 2/7 = 28/63 - 18/63 = 10/63
3) 2/3 : 10/63 = 2/3 * 63/10 = 21/5 = 4,2 (либо 4 целых одна пятая)
2. 5/9 * 6/50 + 5/9 : 100/9 - 5/9 * 2/500 = 13/900
1) 5/9 * 6/50 = 1/15
2) 5/9 : 100/9 = 5/9 * 9/100 = 1/20
3) 5/9 * 2/500 = 1/450
4) 1/15 + 1/20 = 4/60 + 3/60 = 7/60
5) 7/60 - 1/450 = 15/900 - 2/900 = 13/900