а) = 54*( 13/14 * 7*13)=54 * 7/14 = 54 * 1/2 = 27
в) = (12/13 * 13/24)*(14/17 * 17/14)=12/24 * 1= 1/2
д) (21/22 * 22/23)*(24/25 * 23/24)= 21/23 * 23/25 = 21/25
а) = 54*( 13/14 * 7*13)=54 * 7/14 = 54 * 1/2 = 27
в) = (12/13 * 13/24)*(14/17 * 17/14)=12/24 * 1= 1/2
д) (21/22 * 22/23)*(24/25 * 23/24)= 21/23 * 23/25 = 21/25