X\2 + Y\4 = 2X-Y \ 3
( 6X + 3Y) \ 12 = ( 4*(2X-Y) ) \ 12
6X + 3Y = 8X - 4Y
8X - 6X = 3Y + 4Y
2X = 7Y
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X - Y = 1 ---> X = Y + 1
........................................
2*( Y+1) = 7Y
2Y + 2 = 7Y
5Y = 2
Y = 0.4
X = 0.4 + 1 = 1.4
ОТВЕТ: X = 1.4 ; Y = 0.4