CosA=(21^2+23^2-25^2)/2*21*23
cosA=345/966
A=cos^-1(345/966)
A=69.08
If you make a proportion,
12 18
--- = ---
10 x
when you cross multiply
12x=180
x=15
EF= 15
Answer: The answer is 51,208,811
Can we be friends?

and you can expand the numerator if you wish, it won't be simplified further though.