Răspuns:
[tex]((1 + 2 \times 3) \div a + 5) \div 6 = 9 \div 9[/tex]
[tex] \frac{(1 + 2 \times 3) \div a + 5}{6} = 9 \div 9[/tex]
[tex] \frac{(1 + 6) \div a + 5}{6} = 1[/tex]
[tex] \frac{7 \div a + 5}{6} = 1[/tex]
[tex] \frac{ \frac{7}{a} + 5 }{6} = 1[/tex]
[tex] \frac{ \frac{7 + 5a}{a} }{6} = 1[/tex]
[tex] \frac{7 + 5a}{6a} = 1[/tex]
[tex]7 + 5a = 6a[/tex]
[tex]5a - 6a = - 7[/tex]
[tex] - a = - 7[/tex]
[tex]a = 7[/tex]
