Răspuns :

Răspuns:

51 + ( X +23 ) + 26 = 100

( X + 23) +26 = 100 - 51

( X + 23 ) + 26 = 49

( X + 23 ) = 49 - 26

X + 23 = 23

X = 23 - 23

X = 0

1 +2+3+4+X+6+7+8+9=550

10 + X + 30 = 550

X + 30 = 550 -10

X + 30 = 540

X = 540 - 30

X = 510