<span>d:30=200-80</span>
<span>д:30=120</span>
<span>д=120*30</span>
<span>д=3600</span>
<span>3600:30=200-80</span>
<span>120=120</span>
<span><span>140-х=630:7 </span></span>
<span><span>140-х=90</span></span>
<span><span>х=140-90</span></span>
<span><span>х=50</span></span>
<span><span>140-50=90</span></span>
<span><span>90=90</span></span>
<span><span><span>320:а=72:36</span></span></span>
<span><span><span>320:а=2</span></span></span>
<span><span><span>а=320:2</span></span></span>
<span><span><span>а=160</span></span></span>
<span><span><span>320:160=2</span></span></span>
<span><span><span>2=2</span></span></span>