Answer:
Step-by-step explanation:
let 4th fourth vertex be D (x,y)
A(2 1/3,7 1/2),B(12, 7 1/2),C(12,1)
or A(7/3,15/2),B(12,15/2),C(12,1)
Mid-point of diagonal AC is P((7/3+12)/2,(15/2+1))
Mid -point of diagonal BD is P((12+x)/2,(15/2+y)/2)
(Because mid -point of diagonal is same.)
(12+x)/2=(7/3+12)/2
12+x=7/3+12
x=7/3
(15/2+1)/2=(15/2+y)/2
15/2+1=15/2+y
y=1
so fourth vertex is (7/3,1)
