Question 28258
Rene's rate = x+3
Sue's rate = x


Formula:
{{{60/(x+3)-60/x=1}}}
{{{60((x+3)-(x))=(x)(x+3)}}}
{{{60(3)=x^2+3x}}}
{{{x^2+3x-180=0}}}


factor:
(x+15) and (x-12)


remove negative 
x=12


12+3=15


Hence, sue's rate is 12mph and Rene's rate is 15mph.
Paul.