The correct answer to this question is 2/3. As the image shows, there are six triangles in total. Out of those six, four of them are shaded, while two of them are not. This creates the fraction 4/6. A fraction is a quantity that isn't a whole number. This question uses fractions to solve them. With fractions, you break it down until its most reduced to its lowest term.
This is done by reducing the numberation and denominator by the greatest common factor. The greatest common factor of 4/6 is two. Four divided by two is 2 and six divded by two is three. So our original fraction 4/6 reduces down to the fraction 2/3, which is the answer.