Plz help due tomorrow

Quick translate "x is 12 units from 20" into an equation. what are the values of x being described? if you can answer any of my other questions that'd be great too

When constructing a perpendicular line through a point off a line, how can you verify that the lines constructed are perpendicular? check the angles used in the construction with a straightedge to ensure consistency. check the distance along the lines at several places with a compass to ensure they are the same length. check the intersecting lines with the corner of a piece of paper to ensure the lines create 90° angles. check the distance between the lines at several places with a compass to ensure they are equidistant. question 2(multiple choice worth 1 points) (01.03 lc) which of the following steps is included in the construction of a perpendicular line through a point on a line? connect arcs that are above and below the given line with a straightedge. connect arcs that are above the original line with a straightedge. create arcs on either side of a point that is off the given line. create a copied angle by using the first two lines as the original angle.

Given: m< ade = 60° and m< cdf = (3x + 15) prove: x = 15 what is the missing statement and the missing reason in step 5?