From the first and third equations (eliminating y), 4x = 5z - 23,
so z = 21/(1 - 2a) implies x = (105/(1 - 2a) - 23)/4 = (23a + 41)/(2(1 - 2a))
and y = (9 - 2x - z)/2 = -(53 + 41a)/(2(1 - 2a)).

From the first and third equations (eliminating y), 4x = 5z - 23,
so z = 21/(1 - 2a) implies x = (105/(1 - 2a) - 23)/4 = (23a + 41)/(2(1 - 2a))
and y = (9 - 2x - z)/2 = -(53 + 41a)/(2(1 - 2a)).