(x+1)+(x+2)+................+(x+100)=205550
=>x+1+x+2+................+x+100=205550
=>100x+(1+2+3+...........+100)=205550
=>100x+5050=205550
=>100x=205550-5050
=>100x=200500
=>x=200500:100
=>x=2005
( x + 1 ) + ( x + 2 ) + ( x + 3 ) + .... + ( x + 100 ) = 205550
=> x + 1 + x + 2 + x + 3 + .... + x + 100 = 205550
=> ( x + x + x + .... + x ) + ( 1 + 2 + 3 + .... + 100 ) = 205550
=> 100x + { [ 100 . ( 100 + 1 ) ] : 2 } = 205550
=> 100x + [( 100 . 101 ) : 2 ] = 205550
=> 100x + ( 10100 : 2 ) = 205550
=> 100x + 5050 = 205550
=> 100x = 205550 - 5050
=> 100x = 200500
=> x = 200500 : 100
=> x = 2005
Vậy x = 2005