X + y + z = 7

2x - y + z = 7

3x - z = 2

A) X + y + z = 7

B) 2x - y + z = 7

C) 3x - z = 2

C) z = 3x - 2 Substituting this into equations A) and B)

A) X + y + 3x - 2 = 7

B) 2x - y + 3x - 2 = 7 Adding A and B

3x + 6x - 4 = 14

9x = 18

x = 2

Since x = 2 then

A) 2 + y + 6 - 2 = 7

A) y = 1

A) X + y + z = 7

A) 2 + 1 + z = 7

z = 4