THE ANSWER ABOVE IS INCORRECT!! If you are doing Apex, the answer is doubling a cube. It can't be done with a straightedge or compass so it is impossible and was believed to be Apollo wanted something of his doubled with was a cube.
Multiply 2/3 by 8 and you will get 16/3 or 5.33 repeating.
Okay I'm not too sure on this but I believe it is the third one.
I hope this helps!!