1)14*(1/2+1/3+1/4)=
2) 1/3*6/7-1/7*3/4=
3) 1/2*2/3*3/4*5/6*23/24*24/25=

14 * ( 1/2 + 1/3 + 1/4 ) = 14 * ( 6/12 + 4/12 + 3/12 ) = 14 * 13/12 = 91/6 = 15 1/61/3 * 6/7 - 1/7 * 3/4 = 2/7 - 3/28 = 5/281/2 * 2/3 * 3/4 * 5/6 * 23/24 * 24/25 = это уже по действиям решать = 23/1201) 1/2 * 2/3 = 1/32) 1/3 * 3/4 = 1/43) 1/4 * 5/6 = 5/244) 5/24 * 23/24 = 115/5765) 115/576 * 24/25 = 23/120