2.5×5.2÷1.04+77.5
=2.5×4×1.3÷1.04+77.5
=13÷104/100+77.5
=13×25/26+77.5
=12.5+77.5
=90
2.3×25+3÷0.375
=2.3×100÷4+3÷3/8
=57.5+8
=65.5
40÷（1.2+9.3×4）
=40÷[(0.3+9.3)×4]
=10÷9.6
=25/24
4分之3+20分之3×15÷5分之3
=4分之3+20分之3×15×3分之5
=4分之3+4分之15
=4分之18
=4.5