Resposta:
[tex] \frac{b + x}{5} + \frac{b - x}{3} = \frac{ - x}{10} \\ \\ \frac{(b + x) \times 3}{5 \times 3} + \frac{(b - x) \times 5}{3 \times 5} = \frac{ - x}{10} \\ \\ \frac{3b + 3x}{15} + \frac{5b - 5x}{15} = \frac{ - x}{10} \\ \\ \frac{3b + 3x + 5b - 5x}{15} = \frac{ - x}{10} \\ \\ \frac{8b - 2x}{15} = \frac{ - x}{10} \\ \\ 80b - 20x = - 15x \\ 80b = - 15x + 20x \\ 80b = 5x \\ 5x = 80b \\ \\ x = \frac{80b}{5} \\ \\ x = 16b[/tex]
