[tex] \large\underline \bold{{SOLUTION}}[/tex]
Let n be the total of letters and r be the times of repeated letter is.
[tex]\longmapsto\rm{P_n= \frac{n!}{(r!)(r!)(r!)}}[/tex]
[tex]\longmapsto\rm{P_4=\frac{4!}{(1!)(1!)(2!)}}[/tex]
[tex]\longmapsto\rm{P_4=\frac{4×3×2×1}{(1)(1)(2×1)}}[/tex]
[tex]\longmapsto\rm{P_4=\frac{4×3×\cancel{2×1}}{(\cancel{1)(1)(2×1})}}[/tex]
[tex]\longmapsto\rm{P_4=4×3}[/tex]
[tex]\longmapsto\boxed{\rm{P_4=12}}[/tex]
[tex] \large\underline{ \bold{ANSWER}}[/tex]
