<span>х-0,64х=2,808 </span>
<span>0,36х=2,808</span>
<span>х=2,808:0,36</span>
<span>х=7,8</span>
<span>проверка:</span>
<span>7,8-0,64*7,8=2,808</span>
<span>2,808=2,808</span>
<span>
</span>
<span>
</span>
<span><span>7х+9х+0,32=2,72</span></span>
<span><span>16х+0,32=2,72</span></span>
<span><span>16х=2,72-0,32</span></span>
<span><span>16х=2,4</span></span>
<span><span>х=2,4:16</span></span>
<span><span>х=0,15</span></span>
<span><span>проверка:</span></span>
<span><span>7*0,15+9*0,15+0,32=2,72</span></span>
<span><span>2,72=2,72</span></span>