Aini, Nia dan Nisa pergi bersama-sama ke toko buah. Aini membeli 3 kg apel, 2 kg anggur dan 1 kg jeruk dengan harga Rp.79.000,00. Nia membeli 1 kg apel, 2 kg an

3x + 2y + z = 79 (1)
x + 2y + 3z = 69 (2)
x + 3y + 2z = 80 (3)

Eliminasikan (2) dan (3)
x + 2y + 3z = 69
x + 3y + 2z = 80
---------------------- -
-y + z = -11

Eliminasikan (1) dan (2)
3x + 2y + z = 79
3x + 6y + 9y = 207 (persamaan (2) dikali 3)
---------------------- -
-4y - 8y = -128
-y - 2z = -32

-y+z = -11
-y-2z = -32
------------ -
3z = 21
z = 7

-y+7 = -11
-y = -18
y = 18

x + 2×18 + 3×7 = 69
x + 36 + 21 = 69
x + 57 = 69
x = 12

x + 2y + 2z = 12+36+14 = Rp62 ribu