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calculati 5x+7z+2y? stiind ca x+y123 si y+z=257

Răspuns :

5x+ 7z+2y = 5x + 5z+2z+2y= 5(x+y) + 2( z+y)
5x+7z + 2y = 5x123 + 2x257= 615 + 514 = 1129