Depends on your background. I would say it is "medium" Here are the contents Verbal skills - Word knowledge and reading comprehension Mathematics - Basic calculations, word problems, algebra, geometry, conversions, graphs, and applied mathematics Science - General biology, chemistry, physics, and earth science. See more details here
For any test - try to make a "good" guess - which is better than nothing at all. If you really don't know the answer don't try making a random guess - in a 4-choice multiple choice question you only have a 25% chance of being correct for a random guess. There are a few tests that penalize for wrong answers but the PAX does not.