ПОМОГИТЕ ПОЖАЛУЙСТА 20(7/10-3 1/4) -21(2/21+8/21) (2 5/21-22):2/105

1) 20(7/10 - 3 1/4) = 20 (28/40 - 3 10/40) = 20 (28/40 - 2 50/40) = 20 * 2 22/40 = 20 * 2 11/20 = 20 * (2 * 20 + 11)/20 = 20 * 51/20 = (20 * 51)/20 = (1 * 51)/1= 51/1 = 51. Ответ: 51; 2) -21(2/21 + 8/21) = -21 * 10/21 = -(21 * 10)/21 = -(1 * 10)/1 = -10/1 = -10. Ответ: -10; 3) (2 5/21 - 22) : 2/105 = (2 5/21 - 21 21/21) : 2/105 = - 19 16/21 : 2/105 = -415/21 * 105/2 = - (415 * 105)/(21 * 2) = - (415 * 7)/(3 * 2) = -2 905/6 = -484 1/6. Ответ: -484 1/6.