Solve the rational equation: 9aa249+5a+7=1a7\displaystyle \frac{{-{9}{a}}}{{{a}^{{2}}-{49}}}+\frac{{5}}{{{a}+{7}}}=\frac{{1}}{{{a}-{7}}}

Answer: a=\displaystyle {a}=  
Enter your answer as an integer or rational number in the form A/B, using.