Răspuns :
Răspuns: [tex]\purple{\underline{\bf~ a=705~}}[/tex]
Explicație pas cu pas:
[tex]\bf 1200+ 4\cdot \big\{5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2\big\}:3=2012[/tex]
[tex]\bf 4\cdot \big\{5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2\big\}:3=2012-1200[/tex]
[tex]\bf 4\cdot \big\{5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2\big\}:3=812~~~\bigg|\cdot 3[/tex]
[tex]\bf 4\cdot \big\{5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2\big\}=812\cdot 3~~~\bigg|:4[/tex]
[tex]\bf \big\{5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2\big\}=812\cdot 3:4[/tex]
[tex]\bf 5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2=203\cdot 3[/tex]
[tex]\bf 5+2\cdot\big[3\cdot(a-2)+12\big ]:7-2=609[/tex]
[tex]\bf 5+2\cdot\big[3\cdot(a-2)+12\big ]:7=609+2[/tex]
[tex]\bf 2\cdot\big[3\cdot(a-2)+12\big ]:7=611-5[/tex]
[tex]\bf 2\cdot\big[3\cdot(a-2)+12\big ]:7=606~~~\bigg|\cdot 7[/tex]
[tex]\bf 2\cdot\big[3\cdot(a-2)+12\big ]=606\cdot 7~~~\bigg|:2[/tex]
[tex]\bf \big[3\cdot(a-2)+12\big ]=606\cdot 7:2[/tex]
[tex]\bf \big[3\cdot(a-2)+12\big ]=303\cdot 7[/tex]
[tex]\bf 3\cdot(a-2)+12=2121[/tex]
[tex]\bf 3\cdot(a-2)=2121-12[/tex]
[tex]\bf 3\cdot(a-2)=2109~~~\bigg|:3[/tex]
[tex]\bf a-2=703[/tex]
[tex]\bf a=703+2[/tex]
[tex]\red{\underline{\bf~ a=705~}}[/tex]