Question

Tiffiny ate 1 slice of cake. Omer ate 2 slices. If Tiffiny ate 1/5 of the cake and all the slices were the same size, what fraction of the cake remained after Tiffiny and Omer had eaten?

Answer 1

If the total of the slices is one cake, and each slice is 's' in size, then you could model an equation like this:
Total (one cake) = 1 slice + 2 slices + 1/5 slices + remaining cake, or
$c = 1s + 2s + \frac{1}{5}s + R\\ c=2\frac{1}{5}s+R\\ R=2\frac{1}{5}s -c$
Now since I'm sure this question is incomplete, plug in whatever values you need to get the answer.

Answer 2

2/5 of the cake are left. Tiffany ate 1/5 and Omer ate 2x the amount, which is 2/5.