a girl in red pants riding on a moped.
a girl rides moped
a girl in red pants can be simplified to a girl, and rides a moped means riding on a moped.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & in(x1,x2) & on(e1,x4) & n_mope(x4) & Actor(e1,x3) & v_ride(e1) & (x2 = x3) & n_pants(x2) & a_red(s1) & Theme(s1,x2) & n_girl(x1))
exists e1 p1 x1.(exists s1.(Theme(s1,x1) & a_mope(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_ride(e1) & n_girl(x1))