Bài `1:`

`a)19xx61+76xx34`

`=19xx64+19xx4xx34`

`=19xx64+19xx136`

`=19xx(64+136)`

`=19xx200`

`=3800`

`b)35xx12+65xx13`

`=35xx12+65xx12+65`

`=12xx(35+65)+65`

`=12xx100+65`

`=1200+65`

`=1265`

`c)136xx68+16xx272`

`=136xx68+16xx2xx136`

`=136xx68+32xx136`

`=136xx(68+32)`

`=136xx100`

`=13600`

`d)(2+4+6+....+100)xx(36xx333-108xx111)`

`=(2+4+6+....+100)xx(36xx3xx111-108xx111)`

`=(2+4+6+....+100)xx(108xx111-108xx111)`

`=(2+4+6+.....+100)xx0`

`->=0`

`e)19991999xx1998-19981998xx1999`

`=1999xx10001xx1998-1998xx10001xx1999`

`->=0`

Bài `2:`

`a)x:[(1800+600):30]=560:(315-35)`

`x:[1860:30]=560:280`

`x:62=2`

`x=2xx62`

`x=124`

`b)[(250-25):15]:x=(450-60):130`

`[225:15]:x=390:130`

`15:x=3`

`x=15:3`

`x=5`

`c)697:`$\dfrac{15x+364}{x}$`=17`

$\dfrac{15x+364}{x}$`=697:17`

`(15x+364):x=41`

`15x+364=41x`

`364=41x-15x`

`364=26x`

`x=364:26`

`x=14`

`d)92xx4-27=`$\dfrac{x+350}{x}$`+315`

$\dfrac{x+350}{x}$`+315=341`

$\dfrac{x+350}{x}$`=341-315`

$\dfrac{x+350}{x}$`=26`

`x+350=26x`

`25x=350`

`x=350:25`

`x=14`

`e)x-``1/5``+x-``1/7``+x-``1/9``+....+x-``1/35``+x-``1/37``=0`

`(x-1).(``1/5``+``1/7``+``1/9``+....+``1/35``+``1/37``)=0`

Mà `1/5``+``1/7``+``1/9``+...+``1/35``+``1/37``>0`

`⇒x-1=0`

`x=0+1`

`x=1`