The ages of $$A$$ and $$B$$ are in the ratio $$5:7$$ four years from now the ratio of their age $$3:4$$. The present age of $$B$$ is
Correct option is B. $$28$$ years
Let the present ages of A and B be 5x and 7x respectively.
After four years the ratio of their ages is 3:4
$$\implies \dfrac{5x+4}{7x+4}=\dfrac{3}{4}\\\implies 20x+16=21x+12\\\implies x=4$$
The present age of B is 7x=$$7\times 4$$=28years