Resposta:
[tex] \frac{2 - a}{10} + \frac{a - 5}{8} = - \frac{1}{2} \\ \\ \frac{2 - a}{10} + \frac{a - 5}{8} + \frac{1}{2} = 0 \\ \\ \frac{4 \times (2 - a) + 5 \times (a - 5) + 20}{40} = 0 \\ \\ 4 \times (2 - a) + 5 \times (a - 5) + 20 = 0 \\ 8 - 4a + 5a - 25 + 20 = 0 \\ a + 3 = 0 \\ a = - 3[/tex]
