So to put your equation into algebraic terms, your asking for
.
Firstly, we have to convert these into fractional exponents. The rule to do that is
. Applying that here, our equation is

Next, the rule with dividing exponents with the same base is to just subtract the exponents, so with this we are subtracting 1/5 from 1/3. However, we need to find their LCM, or lowest common multiple, of 3 and 5. You can do this by listing out what numbers 3 and 5 are factors of. In this case, the LCM is 15. Multiply 1/3 by 5/5 and 1/5 by 3/3:

Now that they share the same denominator, subtract the numerators of the 2 fractional exponents and your answer will be
, or the last option.