If 1.5a = 0.04b then $$\frac{{b - a}}{{b + a}}$$   is equal to?

$$\eqalign{ & 1.5a = 0.04b \cr & \frac{a}{b} = \frac{{0.04}}{{1.5}} = \frac{4}{{100}} \times \frac{{10}}{{15}} = \frac{2}{{75}} \cr & {\text{Let }}a = 2x,{\text{ }}b = 75x \cr & \therefore \frac{{b - a}}{{b + a}} = \frac{{75x - 2x}}{{75x + 2x}} = \frac{{73}}{{77}} \cr & \cr & {\bf{Alternate:}} \cr & \frac{a}{b} = \frac{{0.04}}{{1.5}} \cr & \therefore \frac{{b - a}}{{b + a}} = \frac{{1.5 - 0.04}}{{1.5 + 0.04}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{1.46}}{{1.54}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{73}}{{77}} \cr} $$