If $\frac{a}{3} = \frac{b}{8}$,then $(a + 3) : (b + 8)$ is equal to

In a mixture of petrol and kerosene,the quantity of petrol is $99 \text{ litres}$. If this same quantity of petrol were present in another mixture of petrol and kerosene where the total volume is $198 \text{ litres}$ less than the actual mixture,the concentration of petrol in the actual mixture would be $13.33 \%$ less than that of the new mixture. What is the concentration (in $\%$) of petrol in the actual mixture?

The ratio of the earnings of $A$ and $B$ is $4:7$. If the earnings of $A$ increase by $50\%$ and those of $B$ decrease by $25\%$,the new ratio of their earnings becomes $8:7$. What are $A$'s earnings (in $Rs.$)?

If $24$ is deducted from $45 \%$ of a number,the result becomes $48$. What will be $\frac{3}{8}$ part of that number?

If $A: B = 3: 4$ and $B: C = 8: 9$,then find the value of $A: B: C$.

If $m : n = 3 : 2,$ then $(4m + 5n) : (4m - 5n)$ is equal to: