Question 846410
The son leaves {{{(1/2)}}} hour after, so The difference in their travel times will be {{{(1/2)}}} hour.  Let d = the unknown distance they travel when the son reaches Sara.


______________speed_________time__________distance
Sara__________45____________t+1/2_________{{{d=45(t+1/2)}}}
Son___________55_____________t____________{{{d=55t}}}



Solve the obvious equation for t, and be aware, the TIME OF THE DAY that the son reaches Sara would be {{{7&1/2+t}}}A.M.