Question

Need help cant figure this out?
3)Solve for x so that b||d.
Picture below

Answer 1

I forget the term for what this is called, but the sum of the angles equals 180. 4x-15+12x+3=180. Solve for x

Answer 2

When given that line b is parallel to line d,
(4x - 15) degrees and (12x + 3) degrees form 180 degrees as a sum - by alternate interior angles property.
Therefore, add them both and equate to 180 to find x.
(4x - 15) + (12x + 3) = 180
4x - 15 + 12x + 3 =180
16x - 12 = 180
16x = 180 + 12
16x = 192
x = 192/16 = 12

Now put the value of x = 12 in both the angles and find their measures.
1. 4x - 15 = 4*12 - 15 = 48 - 15 = 33 degrees, and
2. 12x + 3 = 12*12 + 3 = 144 + 3 = 147 degrees.
Add them both,
33 + 147 = 180 degrees. Therefore, our answer is correct :)