Question

aflati x
2+4+6+.......+98+X=1+2+3+4+5+........+99

Answer 1

2(1+2+3+...+49)+x=1+2+3+...+99
2(49·50)/2 + x = 99·100/2
2450+x=4950
x=4950-2450
x=2500

Answer 2

2(1+2+3+...+49)+x=1+2+3+...+99 => 2*(49*50) : 2 = 99*100 : 2 => 4950-x=99*50
=> 4950-x=2450 => x=4950-2450 = 2500