The formula for determining probability is expressed as
Probability = number of favorable outcomes/number of total outcomes
number of favorable outcomes = number of blue socks = 2
number of total outcomes = number of all socks = 3 + 4 + 2 + 4 = 13
Thus, the probability of picking a blue sock is
2/13 = 0.1538
Converting to percentage, we would multiply by 100. We have
0.1538 x 100
= 15.38%