1) х = 8/9(1/3 - 5/6)
х = 8/9(2/6 - 5/6)
х = 8/9 * (- 3/6)
х = - 4/9
2) х + 8/15 = -20(1/6 - 4/15)
х + 8/15 = -20(5/30 - 8/30)
х + 8/15 = -20 * (-1/10)
х + 8/15 = 2
х = 2 - 8/15
х = 1 7/15
3) у + 3/8 = 4/7(7/20 - 7/8)
у + 3/8 = 4/7(14/40 - 35/40)
у + 3/8 = 4/7*(- 21/40)
у + 3/8 = - 3/10
у = -3/10 - 3/8
у = - 27/40
4) 3/4 + у = -9(5/6 - 8/9)
3/4 + у = - 9(15/18 -16/18)
3/4 + у = - 9 * (- 1/18)
3/4 + у = 1/2
у = 1/2 - 3/4
у = 2/4 - 3/4
у = - 1/4