An elderly man sitting in a chair, eating some snacks.
An old man eating some snacks.
Elderly and old are synonyms.  It is a rephrasing of the original.
exists e2 e1 s1 x1 x2 x3 x4 x5.(a_topic(x1) & Theme(e2,x5) & Actor(e2,x4) & v_eat(e2) & n_snack(x5) & (x1 = x4) & in(e1,x3) & n_chair(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_man(x1) & a_elderly(s1) & Theme(s1,x1))
exists e1 s1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_eat(e1) & n_snack(x3) & (x1 = x2) & n_man(x1) & a_old(s1) & Theme(s1,x1))