Amanda spent a total of $1,440 for lunches during the last 4 months . What is her average cost per month for lunch?

What is the answer to this question? i'm a bit stumped. also how do i do it? 5(x - 4) = 2(x + 5)

Me find the value of x each figure.

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