Solve for u, what is t = v + u for multi variable equations

Write an equation for the function that includes the points (1,4/5) and (2,2/3)

Sum is 17 and their difference is 3

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