Switching gears

Today I began a lesson in our algebra class on solving absolute value inequalities with a straightforward visualization: a skateboarder going a constant 20 ft/s (really? who makes these numbers up?) is coming towards a bystander who is 100 ft away.  When will the skateboarder be 60 ft away from the bystander (who is not moving)?  The class came up with the concept that there are TWO times the skateboarder is 60 ft away, one on each side.  I compared the bystander to Zero on the number line and explained that the absolute value of a number is how far it is from zero.  I wrote absolute value on the board with a definition, and proceeded to show an equation (absolute value of x = 5).  Several students stopped me to say "what is absolute value?"  It totally threw me for a loop because in my mind, I was already headed towards the inequality part of the lesson, and here the students were telling me they didn't know what absolute value was.  I spent much longer than I intended on the basics (since if they don't get those, the rest is useless), and we didn't even START the group quiz that was going to take the last 45 minutes.  Argh!  We plan carefully, but not carefully enough.  It makes me wonder what are they teaching in elementary school?