These two lines create vertical angles, which are congruent. That means angle z = 60 degrees. Since angle z and the angle represented by the expression 6x + 60 are supplementary (they are adjacent angles that add to equal 180 degrees), you can set up the following equation to find x:
6x + 60 + 60 = 180
6x + 120 = 180
6x = 60
x = 10
Answers:
x = 10
z = 60