HELPP ME PLS I NEED IT NOW PLSSS. How could you calculate the x-coordinate of the midpoint of a horizontal segment with endpoints at (0,0) and (20,0)?

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

Aperpendicular bisector, cd is drawn through point con ab if the coordinates of point a are (-3, 2) and the coordinates of point b are (7,6), the x-intercept of cd is point lies on cd.

Im literally having a mental breakdown