Question 1071927
{{{system(r*t=1950,(r+13)(t-5)=1950)}}}


{{{rt+13t-5r-65=1950}}}
{{{rt+13t-5r-65=rt}}}
{{{13t-5r-65=0}}}
{{{13(1950/r)-5r-65=0}}}

{{{13*1950-5r^2-65r=0}}}

{{{-5r^2-65r+13*1950=0}}}

{{{r^2+13r-13*390=0}}}

{{{r^2+13r-5070=0}}}

discriminant is {{{143^2}}}.

{{{r=(-13+143)/2}}}

{{{highlight(r=65)}}}