Refer to the Math Notes box in Lesson 1.2.1 or problem 1-42.
The symbols on two of the lines indicate that those lines are parallel.
The angles marked in the diagram at right are vertical angles, therefore they are congruent.
The value of x can be found because it is supplementary with both 74° angles.
You can also determine the values of angles a through d since they correspond to the angles you have already determined.