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9-78.

Solve for . Each part is a separate problem.

  1. If and , find .

    Angles 1 and 5 are corresponding angles. Since lines and are parallel, the angles are equal.

  2. If and , find .

    Angles 3 and 6 are alternate interior angles. Since lines and are parallel, the angles are equal.

  3. If and , find .

    Angles 4 and 6 are supplementary because the lines cut by the transversal are parallel.

Figure 1: 2 horizontal parallel lines, a, and, b, are crossed by transversal line, t, with angles labeled as follows:  Intersection of a, and t: exterior left, 1, exterior right, 2, interior right, 3, and interior left, b. Intersection of b, and t, interior left, 5, interior right, 6, exterior right, 8, and interior left, 7.