I think it would be the third option. I jiust guessed.
it flies 1666.67 meters in 10 seconds.
Speed = 600km/h
1km = 1000m
1hour = 3600 sec
convert speed in km/h to m/s
600 x 1000/3600 = 6000/36 = 166.667 m/s
Now this speed is for per sec, in 10 sec = 166.667 x 10 = 1666.67m
When u say if u can add or subtract I'm not sure what problem ur referring too. But, maybe this might help.
71x squared is the answer by finding 7x times 11x then 2x times 3x making 77x = 6x minus 6x from 77x and get 71x squared
6x-3(2x-3)=-3
6x-6x+9=-3
0x+9=-3
No Solution