2角=0.2元，1角=0.1元，
设面值0.2元的邮票有x张，则面值0.1元的邮票有（17-x）张，
0.2x+0.1×（17-x）=2.5
 0.2x+0.1×17-0.1x=2.5
              0.1x=2.5-1.7
              0.1x=0.8
                 x=8
则面值0.1元的邮票有：17-8=9（张）．
答：面值0.1元的邮票有9张，面值0.2元的邮票有8张．