（1）（ 9.25+ 0.3×33-1.99）÷2.5
=（9.25+9.9-1.99）÷2.5
=17.16÷2.5
=6.864 （2）（5.7×1.2+1.2×4.3）×2.5
=（5.7+4.3）×1.2×2.5
=10×1.2×2.5
=30
（3）（2.87×9.4-9.4×1.87）×0.13
=（2.87-1.87）×9.4×0.13
=1×9.4×0.13
=1.222 （4）[2.9-1.8÷（ 4.8-3.9）]×3
=[2.9-1.8÷0.9]×3
= （ 2.9-2）×3
= 2.7