Question

I'm having a really hard time figuring out where to start for this problem.

Alex purchased a 6-hour calling card. He has used t minutes of access time. Write an algebraic expressions to represent how many minutes he has remaining and identify units for the expression.

Where do I even start for this one? Also what do they mean by "identify the units"?

Answer 1

The unit your answer will be in is a unit of time, so either hours or minutes. He has a 6 hour calling card, and he has used t minutes.
You're not going to want to work with them if they're in different units, so convert 6 hours to minutes, or t minutes to hours (you choose which one you want to convert to, that's why it says to specify).

Let's convert the 6 hours to minutes. We know that there are 60 minutes in an hour, so 6*60 gives us 360 minutes on his calling card.
Each minute he uses (t) is subtracted from the total minutes he has (360), so your expression is 360 - t minutes.
*The "minutes" is important because it is the unit we chose.

Answer 2

Ohhhh okay that makes sense. So for future reference I should probably convert my problem to have the same units to avoid confusion right?

Answer 3

Definately