Pat, Kate, and Mark charged a total of 135 hours to a certain project. If Pat charged twice as much time to the project as Kate and 1/3 as much time as Mark, how many more hours did Mark charge to the project than Kate?  Choose the correct answer:
A) 18	B) 36	C) 75	D) 90	E) 108

Rationale: 75 all u do is do 2 : 1 : 6 = > 2 x + x + 6 x = 135 = > x = 15 30 : 15 : 90 90 - 15 = 75 answer c
Answer: C