The equation given in the question is
7/(a + 8) + 7/(a^2 - 64 = 7/(a + 8) + 7/(a + 8)(a - 8)
= [7(a - 8)] + 7/[(a + 8)(a - 8)]
= [7a - 56 + 7]/(a + 8)(a - 8)
= (7a - 49)/(a + 8)(a - 8)
= 7(a - 7)/(a + 8)(a - 8)
I hope the procedure of simplification is absolutely clear to you and this is the answer that you were looking for and the answer has actually come to your desired help.