Answer:
T = 2
Step-by-step explanation:
Take the given formulaer
I = PRT
And plug in the variables you know (I, P, R)
387.50 = 1,550(.125)T
(12.5% becomes .125 after you divide it by 100, because precents are really just fractions out of 100)
387.50 = 193.75T
T = 2
She asked her friends, which does not represent a random sample.
She tried to show cause and effect without doing an experiment (which includes simple random sample, control group, treatment, etc).
So the answer is she did not use a random sample, and tried to show cause and effect with an observational study.