Average calculation in same column but for different values

// Of course, your notation is incorrect.
// The formula should read:
//
// 		X = [2A / (B + C)] - 1
//
// In mathematics IT DOES MATTER where you put
// brackets. Note that such a calculation should
// be performed in Power Query, not in DAX.

[New Column] = // column, not a measure
var __code = T[ID Code]
var __a =
	MAXX(
		filter(
			T,
			T[ID Code] = __code
			&&
			T[Type] = "A"
		),
		T[Value]
	)
var __b =
	MAXX(
		filter(
			T,
			T[ID Code] = __code
			&&
			T[Type] = "B"
		),
		T[Value]
	)
var __c =
	MAXX(
		filter(
			T,
			T[ID Code] = __code
			&&
			T[Type] = "C"
		),
		T[Value]
	)
return
	DIVIDE(
		2 * __a,
		__b + __c
	) - 1

// If you want a calculated table,
// you can do this:

[Calc Table] =
ADDCOLUMNS(
	VALUES( T[ID Code] ),
	"X",
		var __code = T[ID Code]
		var __a =
			MAXX(
				filter(
					T,
					T[ID Code] = __code
					&&
					T[Type] = "A"
				),
				T[Value]
			)
		var __b =
			MAXX(
				filter(
					T,
					T[ID Code] = __code
					&&
					T[Type] = "B"
				),
				T[Value]
			)
		var __c =
			MAXX(
				filter(
					T,
					T[ID Code] = __code
					&&
					T[Type] = "C"
				),
				T[Value]
			)
		return
			DIVIDE(
				2 * __a,
				__b + __c
			) - 1
)

Best

D