Given: mAngleADE = 60° and mAngleCDF = (3x + 15)°
Prove: x = 15

3 lines are shown. A line with points E, D, C intersects a line with points A, D, F at point D. A line extends from point D to point B between angle A D C. Angle F D C is (3 x + 15) degrees and angle E D A is 60 degrees.
What is the missing statement and the missing reason in step 5?

A 2-column table with 7 rows. Column 1 is labeled statements with the entries measure of angle A D E = 60 degrees and measure of angle C D F = (3 x + 15) degrees, angle A D E and angle C D F are vertical angles, angle A D E is-congruent-to angle C D F, measure of angle A D E = measure of angle C D F, question mark, 45 = 3 x, and, 15 = x. Column 2 is labeled reasons with the entries given, definition of vertical angles, vertical angles congruent, definition of congruency, question mark, subtractive property, division property.

Statement: 60 = 3x + 15; Reason: substitution
Statement: x = 15; Reason: subtraction property of equality
Statement: 60 = 3x + 15; Reason: transitive property
Statement: x = 15; Reason: subtraction and division properties of equality


Answer is NOT option B.