Adult and child observe fish tank.
two people watching the fish in a tank
One adult and one child together make two people, and both are looking at fish in a tank.
exists s1 x1 x2 x3 x4 x5.(n_tank(x1) & of(x1,x5) & n_fish(x5) & of(x1,x4) & n_observe(x4) & of(x1,x3) & n_child(x3) & a_.(s1) & Theme(s1,x1) & of(x1,x2) & n_adult(x2) & a_topic(x1))
exists e1 x1 x2 x3 x4.(n_fish(x3) & a_topic(x1) & in(e1,x4) & n_tank(x4) & Theme(e1,x3) & Actor(e1,x2) & v_watch(e1) & (x1 = x2) & n_people(x1) & card_eq_2(x1))