Can someone help me with this problem???asap

I'm terrible at math any here is appreciated.

Negative 5 1/12 + negative 4 1/4 + 6 3/4

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