Two people riding dirt-bikes in a somewhat wooded area.
The people are having fun riding dirt bikes by the trees
People can be equal to or more than two people.  Just because people are riding dirt-bikes it does not mean they are having fun.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & in(e1,x4) & n_area(x4) & a_wooded(s1) & Theme(s1,x4) & r_somewhat(x4) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_dirt-bike(x3) & (x1 = x2) & n_people(x1) & card_eq_2(x1))
exists e1 e2 x1 x2 x3 x4 x5.(n_tree(x5) & n_people(x1) & Theme(e2,x2) & Actor(e2,x1) & v_have(e2) & by(x2,x5) & n_bike(x2) & of(x2,x4) & n_dirt(x4) & Actor(e1,x2) & v_ride(e1) & of(x2,x3) & n_fun(x3))