We know that m∠1 and m∠2 are congruent because they are alternate interior angles.
This means that
m∠1 = m∠2
7x = 5x + 30
All you have to do is solve for x. The first thing you do is subtract 5x from both sides.
2x = 30
Now divide both sides by 2.
x = 15
The answer is:
2. 15
