# Paper towels are on sale at 6 rolls for n dollars. How do you write an expression that represents the cost of 4 rolls of paper towels?

The expression would write $4 r = \frac{2}{3} n$ (where r=paper towel rolls).
Let's think about this. Since 6 rolls cost $n$ dollars, that would have to mean that 1 roll costs $\frac{1}{6} n$ dollars. Therefore, we can safely say that 4 rolls cost $\frac{4}{6} n$, or $\frac{2}{3} n$, dollars.