A - reprezinta patratele perfecte
A={1,4,9,16,25,36,49,64,81,100,121,...,infinit}
B - reprezinta multimea nr. naturale nenule, k - multiplu de 5, k impartit la 5 (avem 5:5=1, 10:5=2, 15:5=3 etc)
B={1,2,3,4,5,6,7,8,...,infinit}
C - reprezinta multimea multiplilor lui 3
C={3,6,9,12,15,18,21,24,27,30,33,36,...,infinit}
D - avem inecuatia t-5>1, t>1+5, t>6
D={7,8,9,10,11,12,13,14,15,...,infinit}