Help me with this geo question plss?!!

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?

Answer asap ill give ! ’ a sample of radioactive material decays over time. the number of grams, y , of the material remaining x days after the sample is discovered is given by the equation y = 10(0.5)^x. what does the number 10 represents in the equation? a. the half-life of the radioactive material, in days b. the amount of the sample, in grams, that decays each day c. the time, in days, it will take for the samples to decay completely d. the size of the sample, in grams, at the time the material was discovered

In the sixth grade 13 out of 20 students have a dog if there are 152 sixth grade students how many of them have a dog