A={1,2,3,...,99,100}
B⊂A
{1,2}⊂B⊂{1,2,3,4,....,81}
reunim {1,2} cu fiecare submultime a multimii {3,4,5,6,....,81}
sunt 79 de elemente => multimea {3,4,5,6,....,81} are 2^79 submultimi
=> numarul submultimilor lui B= numarul submultimilor multimii {3,4,5,6,....,81} =2^79
R: 2 la puterea 79