Сделайте деянья 2)(1-4/3):(1/3-1/4); 4)(5/7-2/3):(4/9-5/12);

Необходимо привести дроби к общему знаменателю.

2) (1 - 4/3) : (1/3 - 1/4) = (3/3 - 4/3) : (4/12 - 3/12) = -1/3 : 1/12 = -1/3 * 12/1 = -12/3 = -4;

4) (5/7 - 2/3) : (4/9 - 5/12) = (15/21 - 14/21) : (16/36 - 15/36) = 1/21 : 1/36 = 1/21 * 36/1 =

= 36/21 = 12/7 = 1 5/7;