How do I do this question about indices?

The answer is b^4/a^2
You would subtract the 6 on the top by the 2 on the bottom to help reduce the "B" and then subtract one from the top from the 3 from the bottom as well to again help reduce.
[tex]\frac{b^{4} }{a^{2} }[/tex]
using the ' laws of exponents '
[tex]\frac{a^{m} }{a^{n} }[/tex] = [tex]a^{m - n)}[/tex] if m > n and
[tex]a^{( n - m )}[/tex] if n > m
= [tex]\frac{b^{( 6 - 2 )} }{a^{( 3 - 1 )} }[/tex] = [tex]\frac{b^{4} }{a^{2} }[/tex]