Let's evaluate each equation one by one to determine which one is NOT true.
-
9 + 4 = 13 (not 17)
- False
-
48 + 7 = 55 (not 14 + 31)
- False
-
19 - 8 = 11 (not 20 - 7)
- False
So far, all three equations are false.
Based on the organization of statements, it seems there might be confusion on which statements were intended to compare or be evaluated together.
If we are looking for a truth relative to the entire statement as given, then the first one (9 + 4 = 17) is definitely false.
Therefore, 9 + 4 = 17 is NOT true.
If the intent of your question is more clear, please let me know!