What is the abscissa of the midpoint of the line segment whose endpoints are 1, 2 and 2,3

The abscissa i.e. x coordinate of both the points are 1 from the first point (1,2) and 2 from the second point (2,3). So the abscissa of the mid point is equal = (1+2)/2 = 3/2 = 1.5

Similarly the Y coordinate i.e. the ordinate = (2+3)/2 = 2.5
 Coordinate of the mid point = (1.5,2.5)

The probability of picking 2 green markers is 2/10