3.98÷0.5÷2 (19.3-6.8) ÷4÷2.5
=3.98÷[0.5×2 (19.3-6.8)×4×2.5]
=3.98÷[12.5×10]
=3.98÷125
0.9÷3.05÷2÷0.9×3.05
=0.9*3.05÷3.05÷0.9÷2
=1/2
3.98÷0.5÷2 (19.3-6.8) ÷4÷2.5
=3.98÷[0.5×2 (19.3-6.8)×4×2.5]
=3.98÷[12.5×10]
=3.98÷125
0.9÷3.05÷2÷0.9×3.05
=0.9*3.05÷3.05÷0.9÷2
=1/2