Help me please can't figure it out

Aportion of a line bounded by two points is defined as

In right ∆abc shown below, the midpoint of hypotenuse ac is located at d and segment bd is drawn. if ab = 12 and bc = 16, then explain why bd = 10. hint: consider what you know about the diagonals of a rectangle.

Find the value of x. round the length to the nearest tenth