1) 3 1/7 - 4 7/10 = 22/7 - 47/10 = 220/70 - 329/70 = - 109/70
2) - 109/70 : 1/90 = - 109/70 * 90/1 = - 9810/70 = - 140целых 10/70 = - 140целых 1/7
(5a+5b)/(a^2-b^2)(a^2+b^2):(a+b)/10b=
5(a+b)/(a^4-b^4)*10b/(a+b)=50b/(a^4-b^4)
11⁸-11⁶=11⁶*(11²-1)=11⁶*(121-1)=120*11⁶.
120*11⁶:60=2*11⁶.
120*11⁶:24=5*11⁶.