Answer: she began with 18 because 18 times 2 is 36
Step-by-step explanation:
You can do this by subtracting 6 from 46 because Marissa has 6 less than Trevor. Then you split the remaining 40 into two meaning that each person has 20, but then you add the 6 back to Trevor so the answer is TREVOR HAS 26 T-SHIRTS (and Marissa has 20)