Answer
$\dfrac{1}{x^{\frac{7}{20}}}$
Work Step by Step
Use the rule $\dfrac{a^m}{a^n} = a^{m-n}$ to obtain:
$=x^{\frac{1}{4} - \frac{3}{5}}$
Make the fraction similar using their LCD of 20 to obtain:
$=x^{\frac{5}{20} - \frac{12}{20}}
\\=x^{\frac{5-12}{20}}
\\=x^{\frac{-7}{20}}$
Use the rule $a^{-m} = \dfrac{1}{a^m}$ to obtain:
$=\dfrac{1}{x^{\frac{7}{20}}}$
