5.6+2.8=    3.2×0.4=    6÷100=    740﹣250=    15.28﹣（5.28+5.8）=
18.4÷0.02=    2.36+1.44=    0.46×1000=    3.02×0.8=    1.56×3.5+0.5×1.56=