{3, 4, 7} list all the subsets.

A subset is a collection of items drawn from the original larger set. A subset can have the same number of items as the original set or the count can be smaller. 

Subsets that have 3 items: {3, 4, 7} which is the original set. Any set is a subset of itself. 

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Subsets that have 2 items
{3, 4}, {3, 7}, {4, 7}

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Subsets that have 1 item
{3}, {4}, {7}

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Subsets that have 0 items: the empty set which we write { } or using the symbol [tex]\varnothing[/tex]

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So all together we have 8 subsets
{3, 4, 7}
{3, 4}, {3, 7}, {4, 7}
{3}, {4}, {7}
{ }

Side Note: There are n = 3 items in the original set so there are 2^n = 2^3 = 8 subsets possible. The collection of all subsets is known as a power set.