Question 964174
______________rate_________time__________distance
train__________r____________t____________U
plane_________r+k___________t____________V


UNKNOWNS:  r, t
KNOWNS: k=100,U=80,V=280


{{{system(rt=U,(r+k)t=V)}}}


{{{t=U/r}}}
-
{{{rt+kt=V}}}
{{{r(U/r)+k(U/r)=V}}}
{{{U+kU/r=V}}}
{{{kU/r=V-U}}}
{{{1/r=(V-U)/(kU)}}}
Their reciprocals are then also equal:
{{{highlight(highlight(r=(kU)/(V-U)))}}}