Answer:
Area of polygon = 18
Step-by-step 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