Alright, so in order to solve this problem, you need to know the formula for compound interest, which is
A= P(1+r/n)^nt
A is the final amount, P is the beginning amount, r is the rate it is being compounded at, n is the number of compounds per year, and t is obviously the time or number of years
Since it is compounded monthly, n will equal 12, as there are 12 months in a year.
Plug in what you have and you get A= 100 (1 + .06/12)^(12)(20)
A=331.02
