(х/12+у/5=8
(х/4+у/7=-2
х/12 + 3х/12 + 7у/35 + 5у/35 = 6
4х/12 + 12у/35 = 6
4х/12 = 210/35 - 12у/35
4х/12 = 210-2у/35
4х/12 = 6-12у | ×12
48х=72-144у
48х+144у=72 | ÷48
х+2у=1,5
х = 1,5 - 2у
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(1,5-2у)/4 + у/7 = -2
10,5-14у/28 = - 56/28
10,5-14у+4у = -56
10,5-10у=-56
-10у=-66,5
у=6,65
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х= 1,5-2×6, 65 = 1,5-13,3=-11,8
(-11,8; 6,65)