erna membeli 1 buku tulis ,1 bulpoin,1 buku gambar dikoperasi sekolah. harga 3 buku tulis 1 bulpoin 2 buku gambar Rp20500,00. harga 2 buku tulis 1 bulpoin dan 1

X= buku tulis
Y= bulpoin
Z= buku gambar

3x+y+2z= 20.500....(1)
2x+y+z = 13.500…(2)
x+y+2z = 12.500…(3)
x+y+z= ?

(1)&(2)

3x+y+2z = 20.500
2x+y+z = 13.500
----------------------------- -
x+z = 7.000…(4)

(2)&(3)

2x+y+z = 13.500
x+y+2z = 12.500
--------------------------- -
x-z = 1.000 … (5)

(4)&(5)
x+z = 7.000
x-z = 1.000
------------------ -
2z = 6.000
z = 3.000

x+z = 7.000
x+(3.000)= 7.000
x = 4000

2x+y+z = 13.500
2(4.000)+y+(3.000)= 13.500
8.000+y+3.000 = 13.500
y = 2.500

x+y+z = 9.500