Question 971111
Let avg. speed while going = s
then, avg. speed while returning = s-22 mph
total time taken for trips = 22 hrs
So, 
{{{600/s + 600/(s-22) = 22}}}
{{{600s - 600*22 + 600s = 22*s*(s-22)}}}
{{{1200s - 13200 = 22s^2 - 484s}}}
{{{22s^2 - 1684s + 13200 = 0}}}
{{{s=67.7}}} s= 8.9 not valid since return speed will become negative.
So, speeds while going n returning are 67.7mph and 45.7mph respectively.