I need the resolution of these math matrices

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.

X+ y = 5 ; x - y =3 solve using linear combination

If i have 20$ and i gave 5$ away how much i got