The answer is never, that is, on a 2 dimensional plane. You can perform an experiment to see why it is the case. On curved surfaces though, two lines can intersect one another more than once. For instance, on the surface of planet Earth, two lines can intersect one another, both at the Earth's North Pole and South Pole.
Answer:
You have to take 15 pens to get at least one red pencil.
Step-by-step explanation:
If there were one red and 6 green pens, there would be more red than green pens.
If there were 3 or more blue and thus 18 or more green pens, the number of pens would be over 20.
So there must be 2 blue, 12 green and thus 6 red pencils. So you have to take at least 15 pens to be sure that you got a red one.
Answer:

Step-by-step explanation:
let me know if you want an explanation
Answer:
729 in ^3
Step-by-step explanation:
Answer:
60
Step-by-step explanation: