计算下面各题。
$0.7+9.7+99.7+999.7$
$6+7+8+9+\dots+75$
$28×1111+9999×8$
$8888×16-2222×14$
$98+998+9998+99998+999998+10$

1. $0.7+9.7+99.7+999.7=(1-0.3)+(10-0.3)+(100-0.3)+(1000-0.3)=1109.8$
2. $6+7+8+9+\dots+75=(6+75)×(75-6+1)÷2=2835$
3. $28×1111+9999×8=28×1111+1111×72=(28+72)×1111=111100$
4. $8888×16-2222×14=2222×64-2222×14=2222×(64-14)=111100$
5. $98+998+9998+99998+999998+10=(98+2)+(998+2)+(9998+2)+(99998+2)+(999998+2)=1111100$