If y=3x - 5, find the value of y when x = -1

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

Me because i don't understand how to do it.: )

Need badly. a newborn lion cub weights 3 pounds. each week its weight increases by 5%. create and graph an exponential function to see the cubs growth. thx a ton!