Where did 12x go when factoring the numerator? (i'm not from an english speaking country, so sorry if i used the wrong words, but i hope you'll understand anyway)

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 distance between (0,5) & (-4,2)

Does anyone know how to solve and graph this: 4 + | a + 2 | < 7the only part i don't get is the "4 +"