<span>3х+2х+4х=45см</span>
<span><span>9х=45</span></span>
<span><span><span>х=45:9</span></span></span>
<span><span><span><span>х=5.</span></span></span></span>
<span><span><span><span>5*3=15</span></span></span></span>
<span><span><span><span>5*2=10</span></span></span></span>
<span><span><span><span>5*4=20</span></span></span></span>
<span><span><span><span>Ответ:15см,10см,20см.</span></span></span></span>