x + 18 = 2y; y = 2x – 9

(v) x + 18 = 2y; y = 2x – 9

Sol. x + 18 = 2y

∴  x – 2y = – 18

y = 2x – 9

∴  – 2x + y = – 9

Changing the sign,

∴ 2x – y = 9

D	=	1	-2	=	(1 × -1) – (2 × -2)	=	-1 + 4	=	3
		2	-1

DX	=	-18	-2	=	(-18 × -1) – (9 × -2)	=	18 + 18	=	36
		9	-1

DY	=	1	-18	=	(1 × 9) – (2 × -18)	=	9 + 36	=	45
		2	9

By Cramer's rule,

x	=	Dx	=	36	=	12
		D		3

y	=	Dy	=	45	=	15
		D		3

∴ x = 12 and y = 15 is the solution of given simultaneous equations.