1)х+5/7=(-3/8)*1 1/3
х+5/7=-3/8*4/3
х+5/7=-4/8
х+5/7=-1/2
х=-1/2-5/7
х=-7/14-10/14
х=-17/14
х=-1 3/14
2)у-7/12=3 1/2*(-4/7)
у-7/12=-7/2*4/7
у-7/12=-4/2
у-7/12=-2
у=-2+7/12
у=-1 5/12
3)(-5/14)*21/25-у=3 3/4
-5/14*21/25-у=3 3/4
-1/14*21/5-у=3 3/4
-1/2*3/5-у=3 3/4
-3/10-у=3 3/4
у=-3/10-3 3/4
у=-6/20-3 15/20
у=-3 21/20
у=-4 1/20