Mrs Tay had 425 cookies at first.

After giving Mrs Chan 65 cookies, Mrs Tay had 3 times as many

cookies as Mrs Chan.

How many cookies did Mrs Chan have at first?

425-65=360

360-65=295

Mrs Chan had at first 295 cookies

425 - 65 = 360 (what mrs tay has left.)

360 / 3 = 120 (no. of cookies mrs chan has)

120 - 65 = 55 (cuz mrs chan received the 65 cookies from mrs tay at first)

thus the answer is 55.