1)2.69*3.5=9.415кв.м-первая стена.
<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>
12000/(1270-1267)=4000
1500/5+9070=9370
(1028+679)-789=918