Which is bigger, 40% of 120 or 1/4 of 200

Ineed with number 17 i don’t get it at alll

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z

Which equation represents a direct linear variationa. y=x2b. y=2/5xc. y=1/xd. y=x+3