(6-b)(6+b) / 5(b^2+12+36) = (6-b)(6+b) / 5(b+6)^2 = (6-b) / 5(b+6) = -(b+6) / 5(b+6) = - 1/5
35.....................................
3/4х = - 12 - 2 1/3х = 7/15
х = - 12 : 3/4 - 7/3х = 7/15
х = - 12 * 4/3 х = 7/15 : (- 7/3)
х = - 16 х = 7/15 * (- 3/7)
х = - 3/15
х = - 1/5
18х = 9
х = 9 : 18
х = 0,5