A person with a helmet is riding a bike i the grass and dirt.
Someone is dirtbiking.
A person is someone, and dirtbiking has to occur in the dirt, hence the name, "Dirtbiking."
exists e2 e1 x1 x2 x3 x4 x5 x6 x7.(n_dirt(x7) & n_grass(x6) & subset_of(x7,x5) & subset_of(x6,x5) & Theme(e2,x5) & Actor(e2,x1) & v_i(e2) & with(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_ride(e1) & n_bike(x4) & (x2 = x3) & n_helmet(x2) & n_person(x1))
exists e1 x1.(Actor(e1,x1) & v_dirtbike(e1) & n_person(x1))