(7/10-11/30) * (-1 2/7)+ (1/4 - 11/24) : 2 11/12 = 10/30 * (-9/7) + (6/24 - 11/24) : 35/12 = - 3/7 + (- 5/24) : 35/12 = - 3/7 - 1/14= - 7/14= - 1/2
(7/10-11/30) * (-1 2/7)+ (1/4 - 11/24) : 2 11/12 = 10/30 * (-9/7) + (6/24 - 11/24) : 35/12 = - 3/7 + (- 5/24) : 35/12 = - 3/7 - 1/14= - 7/14= - 1/2