One boy skateboarding on a rail and three boys watching.
The boy skateboarding is teaching the others how to do a trick
You can not infer they do a trick.
exists e2 e1 x1 x2 x3.(Actor(e2,x3) & v_watch(e2) & n_boy(x3) & card_eq_3(x3) & on(e1,x2) & n_rail(x2) & Actor(e1,x1) & v_skateboard(e1) & n_boy(x1) & card_eq_1(x1))
exists e1 p1 x1 x2 x3.(-(x3 = x3) & n_person(x3) & n_skateboarding(x1) & of(x1,x2) & n_boy(x2) & Theme(e1,x3) & Actor(e1,x1) & v_teach(e1) & Topic(x3,p1) & exists e2 x4.(Theme(e2,x4) & Actor(e2,x3) & v_do(e2) & n_trick(x4)))