Bunuel wrote:
In the figure above if \(l_1||l_2\), what is the value of x?
A. 70
B. 100
C. 110
D. 150
E. 170
Attachment:
2018-03-16_1010ed.png [ 10.8 KiB | Viewed 350 times ]
A couple of other ways to approach . . .
\(l_1\) and \(l_2\) are cut by a transversal
Alternate interior angles are congruent.
Lower right angle =
\(40°\)Other angle of lower triangle, given =
\(30°\)1) \(x\) = exterior angle
Exterior angle
\(x\) = sum of opposite interior angles of lower triangle
Exterior angle
\(x\) \(= (30° + 40°) =\) \(70°\)OR
2) Straight line: Third angle of lower ∆ +
\(x = 180°\)Interior angles of a triangle sum to 180°
Lower ∆'s third angle =
\(110°\)(\((180° - 30° - 40°) = 110°\) = third angle))
Third angle lies on a straight line with \(x\)
\(110° + x° = 180°\)
\(x = 70°\)
Answer A
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96% (00:55) correct 
