A boy and girl are dancing.
Two people are dancing.
A boy and a girl are two people.
exists e1 x1 x2 x3.(Actor(e1,x1) & v_dance(e1) & n_girl(x3) & n_boy(x2) & subset_of(x3,x1) & subset_of(x2,x1))
exists e1 x1.(Actor(e1,x1) & v_dance(e1) & n_people(x1) & card_eq_2(x1))