设玲玲有2元纸币x张,则有5元纸币(9-x)张
则2x+5(9-x)=27
2x+45-5x=27
5x-2x=45-27
3x=18
x=6
9-x=9-6=3
答：玲玲有2元纸币6张,则有5元纸币3张