{X + 4y = 9 dengan 3x = -8y + 7. Nilai x dan y?

[1] x + 4y = 9

[2] 3x = -8y + 7

[1] x = -4y + 9

Subtitusikan [1] ke [2]

3(-4y+9) = -8y + 7

-12y + 27 = -8y + 7

20 = 4y

y = 5

Subtitusikan y = 5 ke [1]

x = -4(5) + 9

x = -20 + 9

x = -11