Answer:
Area of polygon = 18
Explanation:
the given points are : 
Point A (2.5) 
 Point B (8,5) 
 Point C (8,9) 
 Point D (5,7) 
 Point E (2,9)
 Firstly , create the array
A 2 5
B 8 5
C 8 9
D 5 7
E 2 9
A 2 5
Now,
Multiply the x coordinates of each vertex by the y coordinate of the next vertex . and then add the result.
⇒ 10 + 72 + 56 + 45 + 10 = 193 .......(1)
Now,
Multiply the y coordinate of each vertex by the x coordinate of next vertex. then add the result
⇒ 40 + 40 + 45 + 14 + 18 = 157 ........(2)
Now, Subtract equation (2) from equation (1), we get
193 - 157 = 36
Now, Divide by 2 to get the area of polygon
∴ we get
Area of polygon = 18