<span>12(x-1)<5x+9</span>
<span>12х-12<span><5х+9</span></span>
<span><span>12х-5х<span><9+12</span></span></span>
<span><span><span>7х<span><21</span></span></span></span>
<span><span><span><span>х<span><21:7</span></span></span></span></span>
<span><span><span><span><span>х<span><3</span></span></span></span></span></span>