Question 881083
Rate*Time=Distance
{{{R[m]=15+R[b]}}}
{{{D=60}}}
{{{T[m]=T[b]-2}}}
.
.
.
1.{{{R[m]*T[m]=60}}}
2.{{{R[b]*T[b]=60}}}

From eq. 1,
{{{(15+R[b])(T[b]-2)=60}}}
From eq. 2,
{{{R[b]=60/T[b]}}}
Substituting,
{{{(15+60/T[b])(T[b]-2)=60}}}
{{{15T[b]-30+60-120/T[b]=60}}}
{{{15T[b]-120/T[b]=30}}}
{{{15T[b]^2-120=30T[b]}}}
{{{15T[b]^2-30T[b]-120=0}}}
{{{T[b]^2-2T[b]-8=0}}}
{{{(T[b]-4)(T[b]+2)=0}}}
Only the positive solution make sense for time,
{{{T[b]-4=0}}}
{{{T[b]=4}}}
Then
{{{R[b]=60/4}}}
{{{R[b]=15}}}
and
{{{R[m]=15+15}}}
{{{R[m]=30}}}
and 
{{{T[m]=4-2}}}
{{{T[m]=2}}}