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11+22+33.....+88-2x=x+12

Răspuns :

11(1+2+3+....8)-2x=x+12 11(8x9/2) -2x=x+12 11x 36-2x = x+12 396-2x=x+12 | -x 396-x = 12 X= 396-12 X= 384