(i just need help filling in the ? with the reason name)

Given: Ray AC is the angle bisector of <BAD, m<BAC = 13x and m<CAD = 6x + 21.

Prove: x = 3.

statement: reasons:
Ray AC bisects <BAD (Given)
m<BAC = 13x (Given)
m<CAD = 6x + 21 (?)
m<BAC = m<CAD (Definition of angle bisector)
13x = 6x + 21 (?)
13x - 6x = 6x - 6x + 21 (Addition/Subtraction Property)
7x = 21 (Substitution Property)
7x/7 = 21/7 (?)
x = 3 Substitution Property

1 answer

statement: reasons:
Ray AC bisects <BAD (Given)
m<BAC = 13x (Given)
m<CAD = 6x + 21 ****GIVEN ****
m<BAC = m<CAD (Definition of angle bisector)
13x = 6x + 21 SUBSTITUION OF VALUES
13x - 6x = 6x - 6x + 21 (Addition/Subtraction Property)
7x = 21 (Substitution Property)
7x/7 = 21/7 MULTIPLY BOTH SIDES BY 1/7
x = 3 Substitution Property