<span>(12у -5у)/4=21</span>
<span>7у=21*4</span>
<span>7у=84</span>
<span>у=84/7</span>
<span>у=12</span>
<span>(19х+6Х)/35=5</span>
<span>25х/35=5</span>
<span>25х=35*5</span>
<span>25х=175</span>
<span>х=175:25</span>
<span>х=7</span>
<span>
</span>
<span><span>234/(21у-8у)=3</span></span>
<span><span>234/ 13у=3</span></span>
<span><span>13у=234/3</span></span>
<span><span>13у=78</span></span>
<span><span>у=78/13</span></span>
<span><span>у=6</span></span>
<span><span>
</span></span>
<span><span>Не сразу поняла,что там 2 уравнения)</span></span>