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LydiaMendes
a fost răspuns

12. (3+6+9+...+30)-(2+4+6+...+20)=?

14.Daca a+b=7, iar b+c=10, aflati a+3b+2c

Răspuns :

Ale2k16
12. (3 +6 +9+...+30) -(2+4+6+...+20)
30×31:2 - 20×21:2 = 930-420= 510