(0.75×57.4-0.574×25+57.4)÷3
=(0.75×57.4-57.4×0.25+57.4)÷3
=57.4×(0.75-0.25+1)÷3
=57.4×（1.5÷3）
=57.4×0.5
=28.7 (0.75×57.4-0.574×25+57.4)÷3
=(0.75×57.4-57.4×0.25+57.4)÷3
=57.4×(0.75-0.25+1)÷3
=57.4×（1.5÷3）
=57.4×0.5
=28.7