A travel agency charges 200 * 75% * x = 150x.

The travel agency fee of B is 200 * 80% * (x-1) =160 x-160.

When the travel agency fees of Party A and Party B are equal,150x = 160x-160, and x =16.

① When the number of people x = 16, the expenses required by the two travel agencies are the same.

② when the number of people is 10 < x < 16, travel agency a needs less expenses.

③ When the number of people is 16 < x < 25, travel agency B needs less expenses.