Răspuns:
[tex]\bf a = -3-2 \cdot(-6)[/tex]
[tex]\bf a = -3+2 \cdot6[/tex]
[tex]\bf a = -3+12[/tex]
[tex]\purple{\bf \underline{~a = 9~}}[/tex]
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[tex]\bf \dfrac{4}{7}: \dfrac{12}{21} = \dfrac{\not4}{\not7}\cdot \dfrac{\not21}{\not12} =\dfrac{1}{1}\cdot \dfrac{\not3}{\not3} =\dfrac{1}{1}\cdot \dfrac{1}{1}=\red{\boxed{\bf ~1~}}[/tex]
