If c=42-d is true, then which is greater: c or d, or are you not able to tell

You cant tell because all you know is that c is less than 42

You can't tell.

Step-by-step explanation:

If d is positive, then it could be either. For example, take the number 3 for d. C is larger in that scenario. If d is 41, then d is obviously greater. If d is negative, then c is always greater.