2) ( х + 8/15) / (1/6 - 4/15) = -20
х + 8/15 = -20*(1/6 -4/15)
х + 8/15 = -20 * ( - 1/10)
х + 8/15 = 2
х = 2 - 8/15
х =22/15
х=1 7/15
3) ( у + 3/8) / (7/20 - 7/8) = 4/7
у + 3/8 = 4/7 * (7/20 - 7/8)
у + 3/8 = 4/7 * (-21/40)
у + 3/8 = - 3/10
у = -3/10 - 3/8
у = - 9/40
4) (3/4 + у) / (5/6 - 8/9) = -9
3/4 +у = -9 * (5/6 - 8/9)
3/4 + у = -9 * ( -1/18)
3/4 + у = 1/2
у = 1/2 - 3/4
у = -1/4