An airplane has a take off speed of 80 m/s which it reaches 35 second after starting from rest. What us the minimum length of the runway?

Use the kinematics formulae:

v = u + at

and

v^2 = u^2 + 2as

where
v is the final velocity,
u is the initial velocity,
a is the acceleration,
t is the time taken
and s is the displacement.