a<b
-2a>-2b
<span> 4<x<5 4<x<5 8<2x<10 </span>
<span><span>1<у<2 -2<-y<-1</span></span>
<span><span>_________ ____________</span></span>
<span><span>4<xy<10 6<2x-y<9</span></span>