Let v be the speed of wind.
1. With the wind a bird flies 3 hours. The speed of bird with the wind is 36+v mi/h.
Then it flies the distance
[tex](36+v)\cdot 3[/tex] miles.
2. Against the wind a bird flies 6 hours with the speed 36-v, then it flies the distance
[tex](36-v)\cdot 6[/tex] miles.
3. If with the wind a bird travels 6 miles farther than against wind, you have an equation
[tex](36+v)\cdot 3=(36-v)\cdot 6+6.[/tex]
4. Solve it
[tex]108+3v=216-6v+6,\\ \\9v=222-108,\\ \\v=\dfrac{114}{9}=\dfrac{38}{3}\approx 12.7[/tex]
5. You find the speed of the wind [tex]v=\dfrac{38}{3}\approx 12.7[/tex] mi/h. Then a bird:
