we are given
Sam packed 42 kg of rice
So, total amount of rice =42kg
And there are six small bags
each contains 1/10 of the rice
So, rice on each bags is

kg
so, total rice in 6 bags is
kg
kg
so, the rice in big bag = ( total amount of rice )-( total rice in six small bags)
we can plug values
and we get
so, the rice in big bag is

kg..............Answer