a motocross bike is jumping through the air between two lines of red tape.
The young girl is competing with a few young men in the motocross competition.
A motocross bike can be ridden by many, not just a young girl.  It can also be ridden for reasons other than competing in a competition.  Also, just because there is on motocross bike does not mean there are also a few young men riding others.
exists e1 s1 x1 x2 x3 x4 x5.(n_air(x3) & between(e1,x4) & of(x4,x5) & n_tape(x5) & a_red(s1) & Theme(s1,x5) & n_line(x4) & card_eq_2(x4) & through(e1,x3) & Actor(e1,x1) & v_jump(e1) & n_bike(x1) & of(x1,x2) & n_motocross(x2))
exists e1 s1 s2 s3 x1 x2 x3 x4.(n_competition(x3) & of(x3,x4) & n_motocross(x4) & n_girl(x1) & a_young(s1) & Theme(s1,x1) & with(e1,x2) & in(x2,x3) & n_man(x2) & a_young(s3) & Theme(s3,x2) & a_few(s2) & Theme(s2,x2) & Actor(e1,x1) & v_compete(e1))