Х+7=3
х=3-7
х=-4
16-х=4
х=16-4
х=12
6-х=15
х=6-15
х=-9
11-х=14
х=11-14
х=-3
-2-х=-5
-х=-5+2
-х=-3
х=3
-х+4=-9
-х=-9-4
-х=-13
<span> 2х+11у=15 </span>
<span>10х-11у=9</span>
<span>Склаадываем, получаем: 12х=24; (11у+(-11у)=0)</span>
<span>х=24:12</span>
<span>х=2</span>
<span>2*2+11у=15</span>
<span>11у=11</span>
<span>у=1</span>
<span>х=2, у=1(2;1)</span>