Question 267119
r*t=d
r*3=18
(r-x)*3=18
r-x=6
(r+x)*3/2=18
r+x=12
r-x=6
2r=18
r=9 in still water
r+x=12
x=3
current=3 

I assume they really mean still water not still air and that they mean boat not plane since they left in a boat not plane.