a + 2b + 2c = 5 …(1)

3a – b + 2c = -4 …(2)

2a + b + c = 15 … (3)

Eliminasi persamaan (1) dan (2)

a + 2b + 2c = 5 (×1) a + 2b + 2c = 5

3a – b + 2c = -4 (×2) 6a – 2b + 4c = -8

_____________ +

7a + 6c = -3 …(4)

Eliminasi persamaan (2) dan (3)

3a – b + 2c = -4

2a + b + c = 15

___________ +

5a + 3c = 11 …(5)

Eliminasi persamaan (4) dan (5)

7a + 6c = -3 (×1) 7a + 6c = -3

5a + 3c = 11 (×2) 10a + 6c = 22

___________ –

-3a = -25

a = 25/3

Substitusi a = 25/3 ke persamaan (5)

5a + 3c = 11

5(25/3) + 3c = 11

125/3 + 3c = 11

3c = 11 – 125/3

3c = 33/3 – 125/3

3c = -92/3

c = -92/3 × 1/3

c = -92/9

Substitusi a = 25/3 dan c = 8/9 ke persamaan (2)

3a – b + 2c = -4

3(25/3) – b + 2(-92/9) = -4

25 – b – 184/9 = -4

b = 25 + 4 – 184/9

b = 225/9 + 36/9 – 184/9

b = (225+36-184)/9

b = 77/9

HP = (25/3 , 77/9 , -92/9)

Semoga membantu.