Matematika kelas 9 no 9 ya

mohon koreksi...
senang bisa membantu :)

4 / 8 = x / (x + 3)
dikali silang
--> 4 x (x + 3) = 8x
--> 4x + 12 = 8x
--> 12 = 8x - 4x
--> 12 = 4x
--> 3 = x