PLEASE ANSWER ASAP REALLY EASY QUESTION WILL GET BRAINLEST Is this a random or biased sample?

Determine the fraction of total interest owed. after the fourth month of a 12-month loan: the numerator is: {(n + ) + (n + ) + (n + ) + (n + )} = , and the denominator is: {(n) + (n + 1) + + (n + )} = . therefore, the fraction is numerator/denominator (to the nearest tenth) =

How to do this , and can some one explain

Which type of graph would allow us to quickly see how many students between 100 and 200 students were treated?