$#Đáp án+Giải thích các bước giải:$
$A/$
`a)210-5x=200`
`->5x=210-200`
`->5x=10`
`->x=10:5=2`
`->x=2`
----------------------------
`b)210:x-10=20`
`->210:x=20+10`
`->210:x=30`
`->x=210:30=7`
`->x=7`
----------------------------
`c)210-5(x-10)=200`
`->5(x-10)=210-200`
`->5(x-10)=10`
`->x-10=10:5`
`->x-10=2`
`->x=2+10=12`
`->x=12`
------------------------------
`d)(2x+1):7=2^2+3^2`
`->(2x+1):7=4+9`
`->(2x+1):7=13`
`->(2x+1)=13.7`
`->2x+1=91`
`->2x=91-1`
`->2x=90`
`->x=90:2=45`
`->x=45`
--------------------------------
`e)450:[41-(2x-5)]=3^2.5`
`->450:[41-(2x-5)]=9.5`
`->450:[41-(2x-5)]=45`
`->41-(2x-5)=450:45`
`->41-(2x-5)=10`
`->2x-5=41-10`
`->2x-5=31`
`->2x=31+5`
`->2x=36`
`->x=36:2`
`->x=18`
------------------------------------
`f)(5x-39).7+3=80`
`->5x-39.7=80-3`
`->5x-39.7=77`
`->5x-39=77:7`
`->5x-39=11`
`->5x=11+39`
`->5x=50`
`->x=50:5=10`
`->x=10`
-------------------------------------------------------
$B/$
`a)400-x.3=100`
`->x.3=400-100`
`->x.3=300`
`->x=300:3`
`->x=100`
----------------------------
`b)250:x+10=20`
`->250:x=20-10`
`->250:x=10`
`->x=250:10=25`
`->x=25`
-------------------------------
`c)96-3(x+8)=42`
`->3(x+8)=96-42`
`->3(x+8)=54`
`->x+8=54:3`
`->x+8=18`
`->x=18-8=10`
`->x=10`
--------------------------------
`d)36:(x-5)=2^2`
`->36:(x-5)=4`
`->x-5=36:4`
`->x-5=9`
`->x=9+5=14`
`->x=14`
----------------------------------
`e)15.5(x-35)-525=0`
`->15.5(x-35)=0+525`
`->15.5(x-35)=525`
`->5(x-35)=525:15`
`->5(x-35)=35`
`->x-35=35:5`
`->x-35=7`
`->x=7+35=42`
`->x=42`
--------------------------------------
`f)[3.(70-x)+5]:2=46`
`->3.(70-x)+5=46.2`
`->3.(70-x)+5=92`
`->3.(70-x)=92-5`
`->3.(70-x)=87`
`->70-x=87:3`
`->70-x=29`
`->x=70-29=41`
`->x=41`
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