The arrangement are:
REA RAE. RED RDE. RAD RDA. ERA. EAR. ERD. EDR. EAD. EDA. ARE. AER. ARD. ADR. AED. ADE. DEA. DAE. DAR. DRA. DAE. DEA

Can you show me the way?
1.List all possible arrangements of the letters RED


We apply the Fundamental Counting Principle (FCP)and multiply:4.3.2=24​