If the average interest rate for a15-year fixed rate mortgage is 5.00%, then the corresponding30-year fixed rate is 4.85%. If the15-year rate decreases to 4.00%, then the30-year rate decreases to 3.75%. what is the equation of the line that describes this relationship. put the answer inslope-intercept form. Let x be the15-year fixed rate and y be the30-year fixed rate. Use the equation to estimate the30-year fixed rate if the15-year fixed rate is 4.5%.