Răspuns: [tex]\color {red}\LARGE \boxed{\bf a = 8}[/tex]
Explicație pas cu pas:
[tex]\large\bf [(a + 7) \cdot 6 - 10] : 4 = 20[/tex]
[tex]\large\bf [(a + 7) \cdot 6 - 10] = 20 \cdot 4[/tex]
[tex]\large\bf (a + 7) \cdot 6 - 10 = 80[/tex]
[tex]\large\bf (a + 7) \cdot 6 = 80+10[/tex]
[tex]\large\bf (a + 7) \cdot 6 = 90~~~\bigg|:6[/tex]
[tex]\large\bf (a + 7) = 15[/tex]
[tex]\large\bf a + 7 = 15[/tex]
[tex]\large\bf a = 15 -7[/tex]
[tex]\color {red}\Large \boxed{\bf a = 8}[/tex]
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