Answer:
[tex]b^{\frac{6}{7}}[/tex] is the required expression.
Step-by-step explanation:
[tex](b^2)^{\frac{3}{7}}\\\\\mathrm{Apply\:exponent\:rule:\:}\left(a^b\right)^c=a^{bc},\:\quad \mathrm{\:assuming\:}a\ge 0\\\\=b^{2\cdot \frac{3}{7}}\\\\=b^{\frac{6}{7}}[/tex]
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