 Luká mwayene ya mbula ya bato oyo: John (17), Laura (18), Robert (19), Edward (20).
 Mwayene ya mbula ya John, Laura, Robert, mpe Edward ezali mbula 18,5. Yango etangami na kosangisaka mibu na bango (17 + 18 + 19 + 20 = 74) mpe kokabola na motango ya bato, oyo ezali 4. Na yango, 74 / 4 = 18,5.