Question 2536
Following formula is used:

Midpoint of a line with endpoints as (x1,y1) and (x2,y2) is ((x1+x2)/2, (y1+y2)/2)

So a line with coordinates (3,7) and (-6,1) will be
X = (3+(-6))/2 = -3/2
and Y = (7+1)/2 = 4

So coordinates of midpoint is (-3/2,4)...hence answer is (a)