Eight and three thirds IS eight and three thirds. It is not an equivalence, it is an identity.
It cant be written as a decimal apart from 3.0 which is a whole number. The fraction is basically saying that there are 9 thirds which equals three. Three thirds equals one because three thirds equals a whole.
"Three thirds" is ONE
three and eight thirty-thirds 3 + 8/33 107/33
Three over eight as a decimal is 0.375
Expressed as a decimal, 8/3 is equal to 2.3 recurring (that is, 2.3333..)