Three workers are working on a metal roof
Three people are working.
people are  workers and they are working on roof
exists e1 x1 x2 x3.(on(e1,x2) & n_roof(x2) & of(x2,x3) & n_metal(x3) & Actor(e1,x1) & v_work(e1) & n_worker(x1) & card_eq_3(x1))
exists e1 x1.(Actor(e1,x1) & v_work(e1) & n_people(x1) & card_eq_3(x1))