Question 174553
Let him start out with {{{x}}} amount of rice
At the first he gives up 1/3 of his rice, so he has
{{{(2/3)*x}}} left
At the second he is allowed to keep 1/3 of what is left,
so now he has
{{{(1/3)*(2/3)*x}}} left
At the third, he gives up 1/4 of what remains, so he gets to keep 
3/4 of what remains. Now he has
{{{(3/4)*(1/3)*(2/3)*x}}}
After passing through all three customs stations, he has 6 pounds less than he started with, so he has {{{x - 6}}}
{{{x - 6 = (3/4)*(1/3)*(2/3)*x}}}
{{{x - 6 = (6/36)*x}}}
{{{x - 6 = (1/6)*x}}}
multiply both sides by {{{6}}}
{{{6x - 36 = x}}}
{{{5x = 36}}}
{{{x = 7.2}}}
He had 7.2 pounds when he started
check:
{{{(3/4)*(1/3)*(2/3)*7.2 = 7.2 - 6}}} 
{{{(1/6)*7.2 = 1.2}}}
{{{1.2 = 1.2}}}
OK