What are two different ways to change the drag on an airplane?

The question seems kind of vague - there are so many ways to change drag on an airplane. But my guess is that they are referring to induced drag and parasitic drag. Check out one of those lift/drag and L/D max charts. Otherwise if thats not what you think they are looking for, think of ways you can change the aircraft's streamline shape in flight. Or what shapes and materials are more and less aerodynamic.

Does sound a bit confusing... SO, how about we take it as really meaning two different changes you can make to an a/c to reduce drag !! So, what are two things you can do the an a/c ?? Like shave all the rivet heads... Reduce joint openings...

The more surface area against the wind = more drag.. for example air/speed brakes slow the aircraft in flight by creating more resistance in the air and spoiling the aerofoil of the wing.. ways you can increase drag on a plane flaps speed/air brakes gear extending (more air resistance) This is on a commercial jet aircraft not propeller. but the forces of flight are the following Lift Gravity Resistance (or drag as you seem to be reffering to) Thrust The greater the speed the greater the air resistance (or drag) acceleration occurs when thrust is greater than air resistance (in aircraft) when air resistance and thrust are the same, and neither can change, the aircraft will stay at a constant velocity, this is called terminal velocity, the maximum speed attainable under its own power (not including gravitational forces)

Drag increases with lift, so you could increase lift and therefore increase.... Or, You could increase parasite drag by not making the surface the air passes over as smooth by putting something out in the slipstream...

Think of driving in a car with the window down and sticking your arm out... the force you feel pulling your arm back is drag... Since drag is a retarding force on the airplane, how can you increase or decrease the retarding force on the airplane?

Lower flaps or drop the landing gear to increase drag. Or you could hang some extra antennae off the fuselage. To decrease drag, wax on, wax off.