`(x+1)+(x+2)+...+(x+100)=5750`
`=> (x+x+x+...+x)+(1+2+...+100)=5750`
`=> 100x+[(100+1).100]/2=5750`
`=> 100x+5050=5750`
`=> 100x=700`
`=> x=7`
`(x+1)+(x+2)+(x+3)+.....+(x+100)=5750`
`x+1+x+2+.....+x+100=5750`
`(x+x+....+x)+(1+2+......+100)=5750`
`100x + 5050 = 5750`
`100x = 5750 - 5050`
`100x = 700`
`x=700:100`
`x=7`