1/x +1/y=3/8 y=8
y=4
СИСТЕМА
x+y=12 x=12-y x=4
x=8
НАХОЖДЕНИЕ Y
1/12-y =1/y=3/8
y+12-y/y(12-y)=3/8
8(y+12-y)=3y(12-y)
8y+96-8y=36y-3y2
3y2-36=96=0(a=3,b=-36,c=96)
D=1296-1152=144
y=36+-12/6
y=48/6 y=8
y=24/6 y=4
ОТВЕТ: х=4 х=8 ; y=8 y=4
ИЛИ (4;8), (8;4)