Question

Harga 8 buah buku dan 6 buah pensil Rp.14.400
Harga 6 buku dan 5 buah pensil Rp.11.200
Maka 5 buah buku dan 8 buah pensil adalah?

Answer 1

8x+6y = 14400 | *5 | 40x + 30y = 72000
6x+5y = 11200 | *6 | 36x + 30y = 67200

(40x + 30y = 72000) - (36x + 30y = 67200)
->4x = 4800
-> x = 4800 : 4
-> x = 1200

6x + 5y = 11200
6 (1200) + 5y = 11200
7200 + 5y = 11200
5y = 11200 - 7200
5y = 4000
y = 4000 : 5
y = 800

5x + 8y = 5 (1200) + 8 (800)
-> 6000 + 6400
-> 12400

Answer 2

Misal ...buku = b......Pensil = P

8b + 6P = 14.400-- x 5---  40b + 30P =72.000
6b + 5p = 11.200--- x 6--  36b + 30p =67.200  -

--------   4b = 4.800--- b = 1.200
   6P = 14.400 - 8 * 1.200 
    6p = 4.800.... P = 800
maka ...5 b + 8 p =
        5* 1.200 + 8*800 = 12.400