Question 69722
I like to use subscripts with these kind of problems
{{{d[1] = r[1]*t}}}
{{{d[2] = r[2]*t}}}
time will be common to both equations (4 hours)
The problems says
{{{d[2] = d[1] + 80}}} at t = 4 
and
{{{r[2] = 2*r[1]}}}
continuing
{{{d[1] = r[1]*4}}}
{{{d[1] + 80 = 2*r[1]*4}}}
substituting
{{{r[1]*4 + 80 = 8*r[1]}}}
{{{4*r[1] = 80}}}
{{{r[1] = 20}}} mi/hr answer
{{{r[2] = 40}}} mi/hr answer
{{{d[1] = 80}}} mi
{{{d[2] = 160}}} mi