So,
5y*3 is the open phrase the student uses to model "the sum of 5y and 3".
"The sum of" means addition.  The student put 5y*3, while the sum of 5y and 3 is actually 5y + 3.
        
                    
             
        
        
        
Answer:
The third one
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
20 mph
Step-by-step explanation:
First problem:
The new speed is 26 mph.
The old speed was x.
The new speed is 30% higher than the old speed.
1.3x = 26
x = 20
Answer: 20 mph
Second problem:
A number, perhaps a percent or a fraction, is missing from the problem.