The two lines y=x and x=-6 intersect on the coordinate plane. What is the value of the area of the figure formed by the intersecting lines and the x-axis?
Choose one:
A) 12
B) 14
C) 16
D) 18
E) 20

Rationale: "the point of intersection is ( - 6 , - 6 ) . the triangle has a base of length 6 and a height of 6 . area = ( 1 / 2 ) * base * height = ( 1 / 2 ) * 6 * 6 = 18 the answer is d ."
Answer: D