agi membeli 3 roti 2 donat = 9000 dikdik membeli 2 roti 1 donat = 5500 berapa harga 2 roti 3 donat?

3r+2d = 9000  |x2|   6r+4d = 18000
2r+d = 5500    |x3|   6r+3d = 16500
                                        d = 1500
3r+2d = 9000
3r+2(1500) = 9000
3r+3000 = 9000
3r = 9000-3000
3r = 6000
r = 6000:3
r= 2000

2r+3d =
2(2000)+3(1500) = 8500

misal :
roti = x
donat = y

3x + 2y = 9000 (i)
2x + y = 5500 (ii)

eliminasi persamaan (i) dan (ii)
3x + 2y = 9000 dikalikan 1
2x + y = 5500 dikalikan 2

3x + 2y = 9000
4x + 2y = 11000
----------------------- -
-x = -2000
x = 2000

3x + 2y = 9000
3(2000) + 2y = 9000
6000 + 2y = 9000
2y = 9000 - 6000
y = 3000/2
y = 1500

1 harga roti = 2000
1 harga donat = 1500
yg ditanya
2 roti + 3 donat =
2(2000) + 3(1500) = 4000 + 4500 = 8500
jadi harga 2 roti dan 3 donat adalah 8500