Rational numbers are numbers which can be written as a fraction (the formula is p/q). They don't include roots we can't solve in order to get a whole number and pi.
A. 776, pi, 25.209, √9 ---> NO (because of pi)
B. 726, 7/34, 20.209, √9 ---> YES
C. √3, 7/39, 20.3, √9 ---> NO (because of √3)
D. 726, 7/34, 20.209, √5 ---> NO (because of √5
Note that √9 = 3, so it IS a rational number.
Answer: centroid
Reasoning: The centroid is the point of concurrency of the three medians in a triangle.
You can use this to help you. label the triangle like the picture and use the equations. I hope this helps.