Jeremy finished 3 puzzles in 168 minutes. the second puzzle took twice as long as the first one and the third pizzle took twice as long as the seond one. how long did the third puzzle take?

The third puzzle took 96 minutes.

Let x be the amount of time the first puzzle took.  Then 2x is the amount of time for the second puzzle, and 2(2x) = 4x is the amount of time for the third puzzle.

We know that together they took 168 minutes:
x+2x+4x=168
7x=168

Divide both sides by 7:
7x/7 = 168/7
x = 24

This is the amount of time for the first puzzle.
The second puzzle took 2x=2(24) = 48 minutes.
The third puzzle took 4x = 4(24) = 96 minutes.