25% of A's income is equal to 35% of B's income. The ratio of the incomes of A and B is -

$$\eqalign{ & = {\text{25}}\% {\text{ of A}} = {\text{35}}\% {\text{ of B}} \cr & \Rightarrow \frac{{25}}{{100}}{\text{A}} = \frac{{35}}{{100}}{\text{B}} \cr & \Rightarrow \frac{{\text{A}}}{4} = \frac{{7{\text{B}}}}{{20}} \cr & \Rightarrow \frac{{\text{A}}}{{\text{B}}} = \frac{7}{{20}} \times 4 = \frac{7}{5} \cr & \Rightarrow {\text{A}}:{\text{B}} = 7:5 \cr} $$