Question 901186
____________________speed__________time_________distance
NORMAL_______________r______________t___________{{{1500=rt}}}
LATE________________r+250__________t-1/2________{{{1500=(r+250)(t-1/2)}}}


r is normal speed which was not used;
t is normal time which was not used;
"not used", because the plane was late starting.
Several steps using the system of equations.