It is given that AB is parellel to CD. These two lines are cut by a transversal, creating angles BAC and DCA. Thus, angle BAC is congruent to angle DCA because alternate interior angles are congruent. It is also given that angle ACB is congruent to angle CAD. Therefore, triangle ABC is congruent to triangle CDA because of the ASA theorem.
Hi,
Work:
Equation;

Factor out 2x from expression.

Use commutative property to reorder yc.

Hope this helps.
r3t40
The answer is x=13 because the equations equal each other
This is how proportion is written 7:21=3:9. The colons are sign of division so it can be shown in the terms of fraction as 7/21=3/9 or 1/3=1/3