The answer is 3/5 simplified.
Reasoning:
There are 6 solid white and solid black marbles combined.
There are total of 10 marbles.
Of the 10 marbles, you are 6/10 times likely to pull one of the solid black or white marbles.
Simplify 6/10 by dividing it by a number they both share (2) to get the answer of 3/5.
