Question 901201
This solution analysis will use time quantities instead of points in time.
Thirty minutes means half hour.


____________________speed____________time___________distance
EARLY_______________250______________t+1/2__________{{{d=250(t+1/2)}}}
LATE________________300_______________t_____________{{{d=300t}}}


Using RT=D rule for uniform rates of travel,


The distance will be equal when the late plane going faster, overtakes
the earlier plane going slower.


Solve for {{{t}}} in the equation, {{{highlight(250(t+1/2)=300t)}}}.
First simplification, {{{5(t+1/2)=6t}}}.