Question 1143883
<pre>
WAY            SPEED         TIME             DISTANCE

DOWNSTR         12+c                            15

BACKUP          12-c                            15

TOTAL                         {{{2&2/3}}}            30
</pre>

Simplify and solve for c:
{{{15/(12+c)+15/(12-c)=2&2/3}}}

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{{{c=3}}}