(3,2 * 5 5/6 - 15,4) * 4 2/7 = 42
1) 3,2 * 5 5/6 = 3,2 * 35/6 = 32/10 * 35/6 = 16/5 * 35/6 = 8/1 * 7/3 = 56/3 = 18 2/3
2) 18 2/3 - 15,4 = 18 2/3 - 15 4/10 = 18 2/3 - 15 2/5 = 18 10/15 - 15 6/15 = 3 4/15
3) 3 4/15 * 4 2/7 = 49/5 * 30/7 = 7/1 * 6/1 = 42