4.2×（6.18-3.03）98.8×3.8÷98.85.4×12-5.4-5.4

⑴4.2×(6.18-3.03)=(4 0.2)×(3 0.15)=12 0.6 0.6 0.03=13.23 ⑵98.8×3.8÷98.8=98.8÷98.8×3.8=1×3.8=3.8 ⑶5.4×12-5.4-5.4=5.4×12-2×5.4=5.4×(12-2)=5.4×10=54 ⑷11÷0.25 19÷0.25=(11 19)÷0.25=30÷0....