How to Solve for Equations?

Question

The accompanying table shows the operating revenue, in millions of dollars, of wired and wireless telecommunications carriers in the United States in the given year.†

Year	Wired	Wireless
2005	205.7	140.0
2006	195.6	157.5
2007	197.0	173.8
2008	194.8	184.8

Calculate the regression line for each type of carrier. (Let t be the time in years since 2005, R be the operating revenue of wired carriers and L be the revenue of wireless carriers. Round your regression parameters to two decimal places.) 

R =

L =

Determine the revenue level at which the two lines cross. Round your answer for the revenue level to one decimal place. 
_________ million dollars

Answer 1

The above spreadsheet shows the data and statistical calculations. The linear regression equations are:

R=202.97-3.13t and L=141.42+15.07t.

The two lines intersect when

202.97-3.13t=141.42+15.07t, 202.97-141.42=15.07t+3.13t,

61.55=18.2t, so t=3.38, the equal revenues are $192.4 million.