What is the correct way of writing: else if (9

the syntax (9<result<16) is appearing to be invalid when I'm using it in my C# code.

I want the else if statement to consider the condition: when the sum of two integers is greater than 9 and less than 16, and return the line :"That's a poor grade" as a result. But the problem is that writing the condition as (9<result<16) is invalid for C#.

So how can I write this condition in code? Please help. I'm new to this :)

Screen shot of code to give you context