Pakai jalannya Y...

6) 5× +2y= 15 2y
saya hnya tau itu

6) 5x + 2y = 15
2y = - 5x + 15
3x + 4y = 23
3x + (2 . 2y) = 23
3x + 2(- 5x + 15) = 23
3x - 10x + 30 = 23
- 7x = - 30 + 23
- 7x = - 7
x = 1 ----> subtitusi :
2y = - 5x + 15
2y = - 5(1) + 15
2y = - 5 + 15
2y = 10
y = 5
hp = { 1, 5} (A)

8) misal
celana = x
baju = y
3x + 2y = 280.000 |×3
x + 3y = 210.000 |×2
9x + 6y = 840.000
2x + 6y = 420.000
-----------------------------(-)
7x = 420.000
x = 60.000
jadi harga sebuah celana = 60.000 (B)

9) misal
ayah = x
anak = y
x = 3y disubtitusi ke :
x - y = 40
3y - y = 40
2y = 40
y = 20
jadi umur anak tsb = 20 th (C)

10) misal
bil 1 = x
bil 2 = y
x + y = 65
x - y = 15
---------------(-)
2y = 50
y = 25
x + y = 65
x + 25 = 65
x = 65 - 25
x = 40
jadi bilangan terkecil = 25 (A)

11) 5A + 2B = 4.000 |×3
2A + 3B = 2.700 |×2
15A + 6B = 12.000
4A + 6B = 5.400
----------------------------(-)
11A = 6.600
A = 600 ----> subtitusi ke :
2A + 3B = 2.700
2(600) + 3B = 2.700
1.200 + 3B = 2.700
3B = 2.700 - 1.200
3B = 1.500
B = 500
jadi
A + B = 600 + 500 = 1.100 (tdk ada opsi)