$${\text{If }}\frac{{3a + 4b}}{{3c + 4d}}{\text{ = }}\frac{{3a - 4b}}{{3c - 4d}}{\text{ then}}$$

Solution (By Examveda Team)

$$\eqalign{ & {\text{According to question,}} \cr & \frac{{3a + 4b}}{{3a - 4b}}{\text{ = }}\frac{{3c + 4d}}{{3c - 4d}} \cr & \Rightarrow \frac{{3a}}{{4b}} = \frac{{3c}}{{4d}} \cr & \Rightarrow ad = bc \cr} $$