Question 43072
j = speed of jetstream
a = speed of plane in still air
against jetstream:
-j + a = 3450/5
with jetstream
+j + a = 8400/8
---------------
do divisions
-j + a = 690
+j + a = 1050
add the equations
2a = 1740
a = 870 km/hr speed of plane in still air
-j + 870 = 690
j = 870 - 690
j = 180 km/hr speed of jetstream
check in  other equation
180 + 870 = 1050
checks