The complete question in the attached figure
we know that
<span>The measure of the external angle is the semidifference of the arcs that it covers.
so
</span><span>m∠BED =(1/2)*[mAC-mBD]-------> solve for mBD
mBD=mAC-2</span>m∠BED
mBD=80-2*25--------> mBD=30°
the answer ismBD=30°
The measure of ∠1 is also <span>93° because vertically opposite angles are equal.</span>
To get it into standard you need to simplify
6y - 12 = -3x add 12 to both sides
6y = -3x + 12 add 3x to both sides
3x + 6y = 12
And that is in standard which is A + B = C