解:設(shè)原分數(shù)的分子為?$x,$?則原分數(shù)的分母為
?$(67 - x)。$?
? $ \frac {x + 4}{67 - x + 9}=\frac {3}{5}$?
?$ 5(x + 4)=3(67 - x + 9)$?
? $ 5x + 20 = 3(76 - x)$?
? $ 5x + 20 = 228 - 3x$?
? $ 8x = 208$?
? $ x = 26$?
?$ $?分母為?$67 - 26 = 41$?
答:原來的分數(shù)是?$\frac {26}{41}。$?