正确答案：
D
解析：
Since the angles marked 7y o and 5y o form a straight line: 7y+5y = 180, 12y = 180, y= 180/12 = 15. An exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent angles. Hence, 7y = 3y+x or x=4y. Since y=15, then x = 60.
