( 1/X ) + ( 1/y ) = 3/8
( X + y ) / xy = 3/8
X + y = 12
y = 12 - X
( X + 12 - X ) / ( x(12 - X )) = 3/8
12/( 12x - x^2 ) = 3/8
8•12 = 3( 12x - x^2 )
8•3•4 = 3( 12х - х^2 )
32 = 12х - х^2
Х^2 - 12х + 32 = 0
D = 144 - 128 = 16 = 4^2
X1 = ( 12 + 4 ) : 2 = 8
X2 = ( 12 - 4 ) : 2 = 4
y = 12 - X
y1 = 12 - 8 = 4
y2 = 12 - 4 = 8
Ответ ( 8 ; 4 ) ; ( 4 ; 8 )