The answer is 4/5
For negative exponents you do the reciprocal of the number and then get rid of the negative sign
For example) To make 5^-2 less complex it can also be written as: 1/5^2 or 1/25
Once it is rewritten as an easier number, you can simply solve the equation:
20 * 1/25
20/25
=4/5
~~hope this helps~~