Question 775528
The original equation is r+s/r+t = 1 + s/t 
:
{{{((r+s))/((r+t))}}} = 1 + {{{s/t}}} 
change it to 
{{{((r+s))/((r+t))}}} = 1 - {{{s/t}}}
Assign values: r=1, t=2; find s
{{{((1+s))/((1+2))}}} = 1 - {{{s/2}}} 
{{{((1+s))/(3)}}} = 1 - {{{s/2}}}
multiply equation by 6
2(1+s) = 6 - 3s
2 + 2s = 6 - 3s
2s + 3s = 6 - 2
5s = 4
s = 4/5
s = .8
:
See if r=1; s=.8; t=2 works in the original equation
{{{((1+.8))/((1+2))}}} = 1 + {{{.8/2}}} 
{{{1.8/3}}} = 1 - .4
.6 = .6, our equation works now