This year
2:7
18:?
well 2*9=18
so 7*9=63
18/63 
(18+63=total 81 students)
Last year
1/8
multiply by 9
9/72
9 less students this year
        
             
        
        
        
The first one is -5
The second one is -4
        
             
        
        
        
Answer:15
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
option D: 27.5 square units
Step-by-step explanation:
Divide the polygon in 6 figures 
see the attached figure
Area of figure 1 (right triangle)
A1=(1/2)(3)(3)=4.5 units²
Area of figure 2 (rectangle)
A2=(1)(3)=3 units²
Area of figure 3 (rectangle)
A3=(1)(3)=3 units²
Area of figure 4 (right triangle)
A4=(1/2)(3)(3)=4.5 units²
Area of figure 5 (right triangle)
A5=(1/2)(4)(5)=10 units²
Area of figure 6 (right triangle)
A6=(1/2)(1)(5)=2.5 units²
The total area is equal to
At=A1+A2+A3+A4+A5+A6
At=4.5+3+3+4.5+10+2.5=27.5 units²
 
        
                    
             
        
        
        
Use the Pythagoras' Theorem:
A^2 + B^2 = C^2
20^2 + 35^2 = C^2
400+ 1225=1625=C^2
square root of 1625= C = 40.31 km