Two teenagers doing tricks on skateboards.
Two first graders are playing on skateboards.
First graders can not be teenagers. Playing is not the same as doing tricks.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x4) & n_skateboard(x4) & Theme(e1,x3) & Actor(e1,x2) & v_do(e1) & n_trick(x3) & (x1 = x2) & n_teenager(x1) & card_eq_2(x1))
exists e1 s1 x1 x2.(on(e1,x2) & n_skateboard(x2) & Actor(e1,x1) & v_play(e1) & n_grader(x1) & a_first(s1) & Theme(s1,x1) & card_eq_2(x1))