Question 790869
The TIME for the trip including all six stops is {{{20/60+6x/60}}} Hour.  Simplified, this time expression is {{{1/3+(x/10)}}} hour.  An adjustment might be needed if the sixth stop is to be AT the final distination, but assuming that the six stops occur BEFORE the final destination, the average rate or speed of 36 km/h can be equated this way:


{{{highlight(21/(1/3+x/10)=36)}}}
Finding the legnth of each stop, x, is fairly simple algebra steps from that.