8     -  20-4aa+5      a^2-25

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Factor second denominator to (a+5)(a-5)Find common denominator of (a+5)(a-5)multiply first fraction by (a-5) because denominator is missing it.   8(a-5)     -       20-4a(a+5)(a-5)       (a+5)(a-5)Now you have 8(a-5)-(20-4a) on top with (a+5)(a-5) on bottom.clean up top:   8a-40-20+4a or 12a-60 remember its over (a+5)(a-5) or8a - 40 - 20 + 4a         or     12a - 60  (a+5)(a-5)                         (a+5)(a-5)factor out a 12 on top to get 12(a-5) all over (a+5)(a-5) or    12(a-5)(a+5)(a-5)now cancel out the (a-5) from both top and bottom    12  (a+5)