(x+1) + (x+2) +(x+3) +(x+4) +.....+ (x+9) + (x+10)= 2015

⇔ x+1+x+2+x+3+x+4+.....+ x+10= 2015

⇔(x+x+x+x+x....+x+(1+2+3+4+...+10)= 2015

Có số x là: (10-1):+1 = 10 số

Ta có : 

10 . x+10 . (10 + 1) : 2= 2015 

10 . x +55 = 2015 

10 . x = 2015-55

10 . x = 1960

⇒ x =1960 : 10

⇒ x = 196

Tìm `x`:

`(x+1) + (x+2) +(x+3) +(x+4) +...+(x+9)+(x+10)= 2015`

`x+1+x+2+x+3+x+4+.....+ x+9+x+10= 2015`

`(x+x+x+x....+x+x)+(1+2+3+4+...+9+10)= 2015`

$\text{Số x là:}$

`(10-1):+1 = 10` $\text{(số)}$

$\text{Ta có:}$

`10* x+10*(10 + 1) : 2= 2015`

`10* x +10*11:2 = 2015`

`10* x +110:2 = 2015`

`10* x +55 = 2015`

`10*x = 2015-55`

`10* x = 1960`

` x =1960 : 10`

`x = 196`

`=> x = 196`

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