Ava swam for 154 minutes during her first week of vacation. In her two weeks of vacation, she swam for a total of 357 minutes. How many more minutes did she swim for in the second week than in the first week? Ava swam for _
more minutes in the second week than in the first week.

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