Question 810315
Use t as target time length if the train were on-time.  There are two speed conditions:


Speed__________________Time hours______________distance miles
40_____________________{{{t+10/60}}}_________________{{{40(t+1/6)}}}
30_____________________{{{t+16/60}}}_________________{{{30(t+4/15)}}}


The distance expressions in the table were both somewhat simplified, and based on {{{Rate*Time=Distance}}}.    These distances are EQUAL, being between two given but unspecified same towns.  We form this equation:


{{{highlight(40(t+1/6)=30(t+4/15))}}}
Solve for t, the target time, and then use it to compute distance between the towns, using either distance expression.