Nrite each expression in the form $2^{kx}$ or $3^{kx}$ for a suitable constant $k$

$($a$)\frac{2^{5x}}{2^{3x}}$

$($b$)\frac{2^{(3x+1)}}{2*2^{-3x}}$

$($c$)\frac{4^{-x}}{8^{-\frac{x}{3}}}$