I cant figure out how to do this question plz help!

Pls! does anybody know a shortcut for answering these types of questions in the future?

The customer price index(cpi), which measures the cost of a typical package of customer goods, was 208.8 in 2011 and 244.1 in 2016.let x=11 corresponding to the year 2011 an estimate to cpi into 2013 and 2014. assume that the data can be modeled by a straight line and the trend to continue idenfinitely. use data points to find such a line and then estimate the requested quantities

Andy has $310 in his account. each week, w, he withdraws $30 for his expenses. which expression could be used if he wanted to find out how much money he had left after 8 weeks?