Помогите ребята решить 15.8

1) a-b/2(b-a) = 1/22) 3x-6y/4y-2x 3(x-y)/2(y-x) = 3/23) m^2-5mn/15n-3m m(m-5n)/3(5n-m) = m/34) 7a^4-a^3b/b^4-7ab^3 a^3(7a-b)/b^3(b-7a) = a^3/b^35) x^2-25/5x^2-x^3 (x-5)(x+5)/x^2(5-x) = x+5/x^26) y^2-12y+36/36-y^2 (y-6)^2/(6-y)(6+y) = y-6/6+y