Concrete road pavement gains strength over time as it cures. Highway builders use regression lines to predict the strength after 28 days (when curving is complete) from measurements made after 7 days. Let x be strenth after 7 days (in pounds per square inch) and y the strength after 28 days.
yhat = 1389 + .96x
Draw a graph of this line, with x running from 3000 to 4000 lbs per square inch.

I don't know how to graph it because the words are confusing me . . . I labed my explanatory (xaxis) as psi from 3000 to 4000 lbs and the response variable (yaxis) as days. How do I graph 1389 (the intercept) on my graph if the yaxis is days?
