The question was asking for the GCF or the Greatest Common Factor
64 = 64×1 = 32×2 = 16×4 = 8×8
56 = 56×1 = 28×2 = 14×4 = 7×8
8 is their common factor and its the highest so 8 is their GCF
The biggest number of cups or glasses that a tray will contain is 8