Since m∠2 and m∠3 are vertical angles, they are congruent. Knowing this, we can form this equation:
5+4y=6y-25 (We'll add the degrees symbol later)
5 = 2y - 25
30 = 2y
y = 15°
We can plug the y-value into the value for m∠2.
5 + 4(15) = 65°
Now, we can easily find m∠1, since they are a linear pair.
m∠1 + m∠2 = 180
m∠1 + 65 = 180
m∠1 = 115°.
m∠1 equals 115°.
Hope this helps!
