У
(6, 10),
(а, 8)
(4, b)
(2, 2)
Х

(2,2)=x1,y1

(4,b)=x,y

(6,10)=x2,y2

using midpoint formula,

y=(y1+y2)/2

y=(2+10+)/2

y=6

which makes (4,b)=(4,6)

again,

(4,6)=x1,y1

(6,10)=x2,y2

(a,8)=x,y

using midpoint formulax=(x1+x2)/2

x=(4+6)/2

x=5

which makes (a,8)=(5,8)

the answer is two. hope this !