First question 
42 students
Second question 65%
        
             
        
        
        
Answer:
 
Step-by-step explanation:
we know that
The simple interest formula is equal to
 
where
A is the Final Investment Value
P is the Principal amount of money to be invested
r is the rate of interest  
t is Number of Time Periods
in this problem we have
 
substitute in the formula above
 
 
 
Remember that Interest is equal to


 
        
             
        
        
        
I’m gonna bet on D. Since I answered your question. Break my ankles✨
        
                    
             
        
        
        
Answer:
10
Step-by-step explanation:
10y+15=7y+45
10y-7y=45-15
3y=30
y=10
hope it helps you!