which set of equations would be used to solve this word problem?

An airplane flew 3 hours with a 30 mph head wind. The return trip with a tail wind of the same speed took 2 hours. Find the speed of the plane in still air.

d = 3(r − 30) and d = 2(r + 30)
d = 3(r + 30) and d = 2(r − 30)
d = 5(r + 30)
None of these systems can be used to solve this problem.

Question

which set of equations would be used to solve this word problem?

An airplane flew 3 hours with a 30 mph head wind. The return trip with a tail wind of the same speed took 2 hours. Find the speed of the plane in still air.
 	
	d = 3(r − 30) and d = 2(r + 30)
	d = 3(r + 30) and d = 2(r − 30)
	d = 5(r + 30)
	None of these systems can be used to solve this problem.

anonymous · Answer

Do you know how to solve it? :)

anonymous · Answer

no. can you help with that?

anonymous · Answer

Yes, I'm trying to figure it out.

perl · Answer

Let r = speed of plane in still air.
In a headwind your speed relative to ground is reduced , this is like a boat traveling up against the current. 
distance = rate * time
d = (r - 30)* 3 
Then on return trip you have a tailwind, so groundspeed is increased.
d = (r + 30)*2

anonymous · Answer

Multiply 3×30×2=180÷3