.
In all cases, the probability is a fraction, whose denominator is the full number of counters.
In each case, the numerator of this fraction is the number of counters under given description.
This hint is enough for you to complete the rest on your own.
For example, in case (a), the answer is
=
=
.
In case (b), the answer is
=
=
.
And so on . . .