[tex]\left( \cfrac{1}{16} \right)^{3-2a}=64^{-a}\implies \left( \cfrac{1}{4^2} \right)^{3-2a}=(4^3)^{-a}\implies (4^{-2})^{3-2a}=4^{-3a} \\\\\\ (4^2)^{2a-3}=4^{-3a}\implies 4^{2(2a-3)}=4^{-3a}\implies 4^{4a-6}=4^{-3a} \\\\\\ 4a-6=-3a\implies -6=-7a\implies \cfrac{-6}{-7}=a\implies \cfrac{6}{7}=a[/tex]
