Question is down below

Answer:
a ) [tex]2 / n[/tex],
b ) [tex]15[/tex]
Step-by-step explanation:
This is a nice and short question we have here.
Given that a bag has n counters, and that one counter is blue, respectively the rest is red, if two counters are taken at random there isn't a definite percentage that one of the counters chosen is red or blue, but there is a fractional representation of this.
We could express n ( number of counters ) to form a probability of 2 / n. As you can see, two counters are taken at random over n counters, and thus we derived this fraction.
a ) [tex]2 / n[/tex]
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Now we have this second part -
[tex]2 / n = 2 / 16,\\16 - 1 = 15[/tex]
Therefore, there are 15 red counters. Hope that helps!