Question 317971
Let Gloria's speed  = {{{s}}}
Then Stacey's speed will be {{{3s}}}
If they are going in opposite directions,
just add their speeds
given:
{{{t = 5}}} hrs
{{{d = 420}}} mi
{{{420 = (s + 3s)*5}}}
{{{420 = 20s}}}
{{{s = 21}}} mi/hr
and
{{{3s = 3*21}}}
{{{3s = 63}}} mi/hr
Stacey's speed is 63 mi/hr and 
Gloria's speed is 21 mi/hr
check:
{{{s + 3s = 21 + 63}}}
{{{s + 3s = 84}}}
{{{420 = 84*5}}}
{{{420 = 420}}}
OK