The cost of travel agency is: 200 x 0.75 =150 x.

The cost of travel agency B is: 200 (x-1) × 0.8 =160 x-160.

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

10x= 160

x= 16

∴ when10 ≤ xat16:160x-160 ∴ choose b travel agency.

When x= 16, you can choose either a or b travel agency.

16 < X≤25,160 x-160 > 150x Choose a travel agency.