\(CaO+H2O-->Ca\left(OH\right)2\)
\(m_{CaO}=70.80\%=56\left(kg\right)=56000\left(g\right)\)
\(n_{CaO}=\frac{56000}{56}=1000\left(mol\right)\)
n\(_{Ca\left(OH\right)2}=n_{CaO}=1000\left(MOL\right)\)
m\(_{Ca\left(OH\right)2}=1000.74=74000\left(g\right)\)= 74kg