Question 323860
Rate*Time=Distance
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When {{{t=0}}} hrs, {{{D=455}}} miles.
When {{{t=3.5}}} hrs, {{{D=0}}} miles.
{{{D=455-(R1*t+R2*t)}}}
{{{D=455-(R1+R2)t}}}
{{{455=(R1+R2)(3.5)}}}
1.{{{R1+R2=130}}}
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You also know, 
{{{R2=R1+10}}}
2.{{{-R1+R2=10}}}
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Add eq. 1 and eq. 2 together to eliminate R1,
{{{R1+R2-R1+R2=130+10}}}
{{{2R2=140}}}
{{{R2=70}}}mph
Then from eq. 2,
{{{-R1+70=10}}}
{{{R1=60}}}mph