Verified answer

As others have said, just keep factoring.

But this isn't so great a way to factor a number. It's better to proceed systematically in increasing prime factors.

72

= 2 * 36

= 2 * 2 * 18

= 2 * 2 * 2 * 9

= 2 * 2 * 2 * 3 * 3

= 2^3 * 3^2

if 72 is written as 6•12

you find another way to write 6 x 12

so 6 = 3x 2

12 = 3x4 = 3 x 2 x 2

72 = 3 x 2 x 3 x 2 x 2

or = 3x3x2x2x2

keep on factoring...

6=2*3

12=2*6=2*2*3

then 72=2*2*2*3*3

that is the solution because none of those factors can be factored any further