Вычислите значение выражения: 1) - 1/4 + 3/5; 5) 7 5/12

1) - 1/4 + 3/5 = (-5+12)/20=7/20;
2) 9/11 + (- 2/5) = (45 + (-22))/55=23/55;
3) - 20/21 + 3/7 = (-20+9)/21=-11/21;
4) - 8 9/14 + 3 3/7 =-5 9/14 + 6/14=-5 3/14;
5) 7 5/12 + (-3 7/24) = 4 5/12 - 7/24=4 10/24 - 7/24=4 3/24=4 1/8;
6) -6 11/12 + (-8 13/18) = -14 + (-33+(-26))/36=-14 + (-59/36)=-15 23/36;
7) - 5 12/35 + 10 = 5 - 12/35=4 23/35;
8) - 11 7/9 + 8 2/15 = -3 7/9 + 2/15=-3 + (-35+6)/45=-3 + (-29/45)= -3 29/45;
9) - 3 1/12 + 1/6 = -3 + (-1+2)/12 = -3 + 1/12=-2 11/12;
10) 3 6/7 + (- 6 4/9) = -3 4/9 + 6/7= -3 + (-28+54)/63=-3 + 26/63= -2 37/63;
11) 9 1/6 + (- 5 3/4) = 4 1/6 - 3/4=4+(2-9)/12=4+(-7/12)=3 5/12;
12) - 3 8/9 + (-2 1/12) = -5 + (-32-3)/36 = -5 + (-35/36)= -5 35/36.