Question 750776
Let x be the age of the youngest of the 6 people.  Then the rest of their ages are 2x, 4x, 8x, 16x, and 32x.

Since their average age is 21, 21*6=126.  The sum of their ages is 126.

{{{x+2x+4x+8x+16x+32x=126}}}

{{{63x=126}}}

Divide both sides by 63:

{{{x=2}}}

So their ages are 2, 4, 8, 16, 32, and 64