The ratio of pencils to erasers is 4: 1 if there are 20 pencils how many erasers are there?

Write the expression 7x^3-28xy^2 as the product of 3 factors

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

How can you find the mean absolute deviation (mad) for this set of data?