Question 830814
Let the rates be {{{R[1]}}} and {{{R[2]}}}.
1.{{{R[1]+R[2]=140}}}
2.{{{15R[1]+5R[2]=1550}}}
From 1,
{{{R[1]=140-R[2]}}}
Substitute into eq. 2,
{{{15(140-R[2])+5R[2]=1550}}}
{{{2100-15R[2]+5R[2]=1550}}}
{{{-10R[2]=-550}}}
{{{highlight(R[2]=55)}}}
Then from eq. 1,
{{{R[1]+55=140}}}
{{{highlight(R[1]=85)}}}