Respuesta :

Answer:

d=200

Step-by-step explanation:

First term

a=9

Second term

a+d=209

Third term

a+2d=409

Fourth term

a+3d=609

Find the common difference (d)

From the second term

a+d=209

a=9

Therefore,

9+d=209

d=209-9

=200

d=200