Which method of data collection would be most appropriate: A study of the effects of new drug intended to treat Dementia.

Really need on these. i have no idea what to do

Which property is illustrated by the following statement? if hxa rgi, then rgi hxa.

Hector and alex traded video games. alex gave hector one fourth of his video games in exchange for 6 video games. then he sold 3 video games and gave 2 video games to his brother. alex ended up with 16 video games. how many video games did alex have when he started?