Draw the line AD and mark the points A, B, C and D on it.

Given in the question B is the mid-point of AC and C is the mid-point of BD.

From the above statement we get,

AB = BC…(i) (mid-point: a mid-point divides a line into two equal parts)

BC = CD…(ii) (mid-point)

From the first and second statements we can say that,

AB = CD