3/7×5/11=15/77; 6/25×5/18=1/5×1/3=1/15; 2 1/10×1 1/14=21/10×15/14=3/2×3/2=9/6=1 3/6=1 1/2; 3 3/5×1 1/9=18/5×10/9=2/1×2/1=4/2=2; 1 3/7×14=10/7×14/1=140/7=20
42 9/11 ему противоположное число(-42 9/11)
-0,25y = 1,5
y = 1,5 / (-0,25)
y = (-6)
(6/7 - y) + 2/7 = 5/7
6/7 - y = 5/7 - 2/7
6/7 - y = 3/7
y = 6/7 - 3/7
y = 3/7
(6/7 - 3/7) + 2/7 = 5/7
5/7 = 5/7
{20 - (3а - 7)} /10 = 9/10
20 - (3а - 7) = 9/1 = 9
20 - (3а - 7) = 9
3а - 7 = 20 - 9
3а - 7 = 11
3а = 7 + 11
3а = 18
а = 18 : 3
а = 6