Hey there! :)
2 red , 3 white , 1 blue = a total of 6 marbles
If 2 marbles are drawn from the bag, then that's 2 marbles out of six.
So, our probability is 2/6. However, because there are 3 white marbles, this gives us a higher probability that 2 of those six marbles pulled are white.
So, our final probability is 3/6 , or 1/2 simplified.
~Hope I helped!~