So, first things first, you need to get a common denominator for the two fractions.
That would be 40.
[tex] \frac{4}{5} \times \frac{8}{8} = \frac{32}{40} [/tex]
[tex] \frac{3}{8} \times \frac{5}{5} = \frac{15}{40} [/tex]
Which one is larger?
By how much is it larger?
Remember to reduce.