Let x and y be the numbers;
We have x + 2y = 9 and 2x + y = 21;
Then, x = 9 - 2y;
Finally, 2(9-2y) + y = 21 ;
18 - 4y + y = 21;
18 - 3y = 21;
-3y = 3;
y = - 1;
x = 9 - 2× (-1);
x = 9 + 2 ;
x = 11;
        
             
        
        
        
<h2>
Explanation:</h2>
The complete question is in a comment above. The statements says that:
- Sean wrote the equation  
 is the cost per pound. is the cost per pound.
- The equation show the relationships between the total cost, $9.25, and the number of pounds of pears.
So we are asked to write an write an equation to show the cost y of x pounds of pears. In other words, we need to write an equation such that y is given in terms of x, where x is the pounds of pears. So:

From the equation we can determine  as:
 as:

So each pound costs $1.85. The equation tells us that 5 pounds of pears result costs $9.25. Then, by proportion:

So choosing the number of pounds as 0, 1, 2, 3, 4, 5, the table would be:

From the table we can know that the graph is a line. that passes through all these points. Since this line passes through the origin, then y varies directly as x (Direct Proportion).
 
        
        
        
I’m guessing red at this point-