Answer:
1/12
Step-by-step explanation:
You are close but 1/27 includes people who did not study but still passed. If you want a singular value you should look at the value for the for only the people who studied even if they passed. 
 
        
             
        
        
        
Any number that you can completely write down on paper using digits ... and a fraction bar or decimal point if necessary ... is a rational number.  If you add it to 0.5, then the sum is another rational number. 
 
        
             
        
        
        
Área of rectangle= 18 x 14 = 252
Area or triangle=
30-18= 12
12 is the base of the triangle 
14 is the height of the triangle 
Area of a Triangle= 1/2bh
1/2(12)(14)=84
Área of Triangle= 84 
252+84= 336
Answer= 336
        
             
        
        
        
Do you have any graphs because that would be more clear