<span>15 см</span>²=15*10*10 мм²=1500 мм²
<span>8 м</span>²=8*10*10 дм²=<span>800 дм</span>²
<span>3 м</span>²=3*100*100 см²=30000 см²
<span>23 м</span>²<span> =23*10*10 дм</span>²=<span>2300 дм</span>²
8,7-(70+8,7)=8,7-70-8,7=-70
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a-7+y+14=a+y+7
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-12+(x-30)=-6
-12+x-30=-6
x=-6+12+30
x=36
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