Interleaved input / output

If a program should double its input, an instructor might provide this example:

Enter x:
5
x doubled is: 10

Students often incorrectly create a program that outputs the 5. Instead, the program should only output the output parts:

Enter x:
x doubled is: 10

The instructor's example is showing both the output of the program, AND the user's input to that program, assuming the program is developed in an environment where a user is interacting with a program. But the program itself doesn't output the 5 (or the newline following the 5, which occurs when the user types 5 and presses enter).

Also, if the instructor configured the test cases to observe whitespace, then according to the above example, the program should output a newline after Enter x: (and possibly after the 10, if the instructor's test case expects that).

The program incorrectly echoes the user's input to the output.