<u><em>Надо 4,6 * 500000 = 2300000 см = </em></u><em>23 км</em>
<span>3х + 7х + 18 = 178,</span><span>10х + 18 = 178,</span><span>10х = 178 – 18,</span><span>10х = 160,</span><span>х = 160 : 10,</span><span>х = 16,</span><span>Ответ: х = 16.</span>