I think it is either 10 or 11
(4^2+8^2)^.5 = 8.944
It's not 12.
So 4,8,12 can't be the side lengths of a right triangle.
You mean to simplify as this is an expression not an equation, as it has no equal sign...
Factor our 4 first
(4r^3t^2)/(-rt)
Now factor out -rt
-4r^2t
