Question 598776
{{(a-4)(a+3)/a^2-a} ÷ {2(a-4)/(a+3)(a-1)}}
Invert the divisor and multiply 
= {{{((a-4)(a+3)/(a^2-a)) * (a+3)(a-1)/(2(a-4))}}} 
Cancel the (a-4)
= {{{((a+3)/(a^2-a)) * (a+3)(a-1)/2}}} 
Factor a^2-a
= {{{(a+3)/(a*(a-1)) * (a+3)(a-1)/2}}}
Cancel (a-1)
= {{{(a+3)/(a) * (a+3)/2}}}
= {{{(a+3)(a+3)/2a}}}
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If you showed your attempts, you'd get an answer sooner, rather just posting it repeatedly.
Doing it for you is not tutoring.