We know that 2/3 dislike lima beans, and 3/5 of these dislike brussel sprouts. So we know what percent of the students like lima beans, (1/3) but we have no idea what ratio likes brussel sprouts. We know that 3/5ths of those that don't like lima beans also don't like brussel sprouts, but of the kids that like lima beans you could have 100% of those liking brussel sprouts, or a 100% not liking brussel sprouts.
1) Insufficient. Giving us the total number still doesn't tell us how many of those that like lima beans also like brussel sprouts. It lets us know that 40 students like lima beans, and that 2/5ths of 80, or 32, students that don't like lima beans also don't like brussel sprouts, but we still don't have a total without that number or ratio missing for the students that like lima beans.
2) Insufficient. This basically gives us the same information as 1. 40 is 1/3 of 120, so we already knew this, but again, gets us no closer to knowing how many of those 40 like or dislike brussel sprouts, no ratio, fraction or percentage was given for this 1/3 of the students.
Hope that helps, sorry if it was a little long winded.