What number should be added to each of 6, 14, 18 and 38

What number should be added to each of 6, 14, 18 and 38 so that the resulting numbers make a proportion ?

6 + x	=	18 + x
14 + x	=	38 + x

From the given alternatives

6 + 2	=	18 + 2
14 + 2	=	38 + 2

⇒	1	=	1
	2		2

Second Method :
Here, a = 6, b = 14, c = 18, d = 38

Required number x =	bc − ad
	(a + d) − (b + c)

=	14 × 18 − 6 × 38
	(6 + 38) − (14 + 18)

=	252 − 228
	44 − 32

=	24	= 2
	12